preservative treatment of timber€¦ · for timber preservatives, the preparation of timber for...

DRAFT UGANDA STANDARD

DUS 2021

First Edition 2019-04-24

Reference number WDUS 2021:2018

© UNBS 2018

Preservative Treatment of Timber

WDUS 2021:2019

ii © UNBS 2018 – All rights reserved

Compliance with this standard does not, of itself confer immunity from legal obligations

A Uganda Standard does not purport to include all necessary provisions of a contract. Users are responsible for its correct application

© UNBS 2019

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilised in any form or by any means, electronic or mechanical, including photocopying and microfilm, without prior written permission from UNBS.

Requests for permission to reproduce this document should be addressed to

The Executive Director Uganda National Bureau of Standards P.O. Box 6329 Kampala Uganda Tel: +256 414 333 250/1/2/3 Fax: +256 414 286 123 E-mail: [email protected] Web: www.unbs.go.ug

mailto:[email protected]

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© UNBS 2021 – All rights reserved iii

Contents Page

Foreword ............................................................................................................................................................. v

The preservative treatment of timber ............................................................................................................... 1

1 scope ................................................................................................................................................................ 1

2 Normative references ............................................................................................................................ 1

3 Terms and Definitions ........................................................................................................................... 2

4 Classification and properties of timber preservatives ................................................................................ 3 4.1 Classification ................................................................................................................................................ 3 4.2 Properties ...................................................................................................................................................... 4

6 Preparation of timber for treatment ............................................................................................................... 8 6.1 General .......................................................................................................................................................... 8 6.2 Sorting ........................................................................................................................................................... 8 6.2.1 Species ....................................................................................................................................................... 8 6.2.2 Dimensions ................................................................................................................................................ 8 6.2.3 Timber defects ........................................................................................................................................... 8 6.3 Seasoning ..................................................................................................................................................... 8 6.3.1 General ....................................................................................................................................................... 8 6.3.2 Moisture content ........................................................................................................................................ 8 6.3.3 Prevention of insect attack during seasoning ....................................................................................... 9 6.3.4 Prevention of mould attack ...................................................................................................................... 9 6.4 Surface preparation ...................................................................................................................................... 9 6.5 Shaping ......................................................................................................................................................... 9 6.6 Incising .......................................................................................................................................................... 9 6.6.1 General ....................................................................................................................................................... 9 6.6.2 Methods .................................................................................................................................................... 10

6.7 Stacking ....................................................................................................................................................... 10

7 Preparation and control of preservative mixtures ..................................................................................... 10 7.1 General ........................................................................................................................................................ 10 7.2 Mass concentration .................................................................................................................................... 10 7.3 Toxicity and safety ..................................................................................................................................... 10 7.4 Flammability ................................................................................................................................................ 10

8 Application methods for preservatives ....................................................................................................... 11 8.1.1 Surface brushing and spraying ............................................................................................................. 11 8.1.2 Immersion, steeping, deluging .............................................................................................................. 11 8.2 Prescribed timber-preservative treatment processes ............................................................................ 11 8.2.1 General ..................................................................................................................................................... 11 8.2.2 Diffusion ................................................................................................................................................... 11 8.2.3 Gas phase process.................................................................................................................................. 12 8.2.4 Hot or cold open tank process ............................................................................................................... 12 8.2.6 Low-pressure process ............................................................................................................................ 13 8.2.7 The vacuum impregnation (double vacuum) process ......................................................................... 14

8.3 Equipment required .................................................................................................................................... 14

9 Handling and safety of preservative-treated timber .................................................................................. 15 9.2 Safety ........................................................................................................................................................... 15 9.3 Fixation of WCCA preservatives ............................................................................................................... 15 9.4 Disposal ....................................................................................................................................................... 15 9.5 Flammability ................................................................................................................................................ 15 9.6 Safety handling information labelling ...................................................................................................... 16

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iv © UNBS 2018 – All rights reserved

10 Penetration and net retention .................................................................................................................... 16

11 Recommendations for the use of timber preservatives in specific applications ................................ 24 11.1 Contact with food..................................................................................................................................... 24 11.1.1 Direct contact with food for human consumption ............................................................................ 24 11.1.2 Direct contact with feeds for livestock ............................................................................................... 24 11.1.3 Indirect contact with food or feeds ..................................................................................................... 24 11.2 Human contact ......................................................................................................................................... 24 11.3 Animal contact ......................................................................................................................................... 24 11.3.1 Continuous direct contact ................................................................................................................... 24 11.3.2 Periodic direct contact ......................................................................................................................... 25 11.4 Contact with plants .................................................................................................................................. 25 11.5 Combustion gases ................................................................................................................................... 25 11.6 Timber for use in cooling towers ........................................................................................................... 25

12 The use of preservative-treated timber in specific areas in Uganda .a................................................. 25 12.1 Qualification ............................................................................................................................................. 25 12.2 Gymnospermae (coniferous species) ................................................................................................... 25 12.3 Angiospermae (broadleaved species .................................................................................................... 25 12.4 Preservative treatment ............................................................................................................................ 26

13 Treatment plant area compliance .............................................................................................................. 26

Bibliography ..................................................................................................................................................... 49

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© UNBS 2021 – All rights reserved v

Foreword

Uganda National Bureau of Standards (UNBS) is a parastatal under the Ministry of Trade, Industry and Cooperatives established under Cap 327, of the Laws of Uganda, as amended. UNBS is mandated to co-ordinate the elaboration of standards and is

(a) a member of International Organisation for Standardisation (ISO) and

(b) a contact point for the WHO/FAO Codex Alimentarius Commission on Food Standards, and

(c) the National Enquiry Point on TBT Agreement of the World Trade Organisation (WTO).

The work of preparing Uganda Standards is carried out through Technical Committees. A Technical Committee is established to deliberate on standards in a given field or area and consists of key stakeholders including government, academia, consumer groups, private sector and other interested parties.

Draft Uganda Standards adopted by the Technical Committee are widely circulated to stakeholders and the general public for comments. The committee reviews the comments before recommending the draft standards for approval and declaration as Uganda Standards by the National Standards Council.

The committee responsible for this document is Technical Committee UNBS/TC 12, furniture.

DRAFT UGANDA STANDARD DUS 2021:2018

© UNBS 2018 – All rights reserved 1

The preservative treatment of timber

1 scope

This standard covers the classification of timber preservatives, hazard conditions for timber, the solvents used

for timber preservatives, the preparation of timber for treatment, the various treatment processes and the use

of preservative-treated timber in specific areas in Uganda. Recommendations relating to the handling and

safety of preservative-treated timber are also given. This standard does not cover treatment with fire

retardants.

2 Normative references

The following referenced documents referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

DUS 1722, Eucalyptus poles, cross-arms and spacers for power distribution and telephone systems.

DUS 2084, Heartwood detection in timber of pinus species

DUS 2018, Retention of preservative in timber (sample method).

DUS 2013, Retention of preservative in timber (volume method)

DUS 2019, Retention of preservative in timber (weighbridge method).

DUS 2016, Moisture content of timber (electric moisture meter method)

DUS 2014, Moisture content of timber and timber products (oven dry method)

DUS 2015, Moisture content of timber (extraction method)

DUS 2017, Depth of penetration of preservative and detection and depth of sapwood in timber

US EAS 323 Specification for wood preservation by means of pressure creosoting

US EAS 324 Copper/chromium/arsenic compositions for the preservation of timber — Method for timber treatment

2 © UNBS 2019 – All rights reserved

3 Terms and Definitions

For the purposes of this document, the following terms and definitions apply 3.1.

acceptable acceptable to the authority administering this standard, or to the parties concluding the purchase contract, as relevant

3..2

afterglow phenomenon where ignited timber keeps on glowing after having been set alight and after the original source of ignition has been removed; this slow combustion could eventually lead to the total destruction of the timber

3..3

average net retention <assay zone> mass of all active components of a preservative compound retained in the zone of timber to be treated

3..4

average net retention <total volume> mass of all active components of a preservative compound (where relevant, including water of crystallization) retained in the total volume (not the penetrated volume) of timber

3.5

bleeding exudation of liquid preservative chemical on a surface of preservative-treated timber

3..6

charge quantity of timber treated in one and the same treating cycle

3..7

inner bark physiologically active layer of tissues between the cambium and the phellogen, plus any cells of the phloem that remain alive

3..8

marine treatment treatment of timber that will be constantly in contact with estuarine or sea water and therefore subject to marine borer attack

3..9

outer bark layer of dead tissues (generally of a dry corky nature) outside the phellogen

3.10

permanent building structure in which people live, work or play or in which animals are accommodated or in which goods are preserved, worked, manufactured, processed, stored or sold; as well as a bridge, cooling tower, water tank tower, watch tower, pylon, water work or similar structure for which a plan is to be approved in terms of one or other provision in legislation before the construction

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3.11

structural timber all timber of the botanical group Gymnospermae (coniferous species and Angiospermae (broadleaved species (see 12.3)), which forms part of a permanent building or which is destined to form part of a permanent building, for example, but not limited to roof structures, frame-wall construction, flooring, paneling, window frames and door frames

3.12

timber-preservative treatment pesticidal agent that, when impregnated into or otherwise applied to timber, renders the timber less susceptible to destruction by fungi, insects or marine borers

3..13

timber protectant agent that is fungicidal or insecticidal or both, and that is applied to timber to protect it temporarily from attack during one or more stages of processing

3.14 volatile solvent timber-preservative solvent, at least 90 % of the volume of which evaporates from the treated opens tacked timber within an acceptable period after treatment

3.2 Abbreviations

HCS hazardous chemical substance

LOSP light organic solvent preservative

MSDS material safety data sheet

4 Classification and properties of timber preservatives

4.1 Classification

For the purposes of this standard, timber preservatives1) are classified as shown in table 1. NOTE The determination of the class and type of a timber preservative is based on the chemical constitution of the preservative components or of the treatment solution. Classification based on a qualitative analysis of components present

in the preservative or in the treated timber is possible in specific cases and should be such as to be acceptable.

Table 1 — Classification of timber preservatives

1 2 3

Class of preservative Type of preservative Description

C CCHT

CCL

CCWO

Oil

Creosote – High-temperature

Creosote – Lurgi-gasification process

Mixtures of creosote and waxy oil

W WCCA

WB

WCuAz

Waterborne

Mixtures of copper-chromium-arsenic compounds Borate

Mixtures of copper azole compounds


O OB

OTBTOL

OTBTNP

OZP

Light organic solvent preservatives (LOSPs)

Borate

Tributyltin oxide-lindane

Tributyltin napthenate-permethrin

Azole-permethrin

O OI-D LOSPs – Insecticides

Deltamethrin

4.2 Properties

4.2.1 Class C: coal tar creosote and timber preservatives with a coal tar creosote basis. Class C consists of preservatives that contain distillates of coal tar, with or without a waxy oil additive. The preservatives are complex mixtures of a large number of compounds, and certain characteristics are defined

in the relevant standards. 1) Timber protectants are not included in the table. See also the last paragraph of the introduction. Properties of preservatives of this class include the following: a) the preservatives are normally resistant to leaching and are therefore particularly suitable for exterior conditions (see 5(c) and (d)), and for interior work, except where their odour is objectionable; b) the preservatives are not corrosive to metals but are highly flammable at normal treating temperatures (see 8.2.4, 8.2.5 and 9.5); c) no change in the dimensions or in the shape of timber results from creosote treatment; d) freshly creosoted timber cannot normally be painted; a bituminous-based aluminium paint or epoxy-based paint can be used on timber after it has been exposed for a few months, but other paints can be applied only after some years of exposure; e) creosote is oily and dark in colour, and has a characteristic odour that can be absorbed by foodstuffs and other materials in the vicinity without their actually coming into contact with the creosoted timber; f) if applied to timber to a high retention, creosote is liable to bleed during the first few months after treatment, especially during hot weather (if this would be objectionable, an empty-cell process is recommended (see 8.2.5.3 and 8.2.5.4)); and g) creosoted timber can stain plaster and other absorbent materials with which it comes into contact.

4.2.2 Class W: solutions of compounds in water

4.2.2.1 General

When required, timber treated with waterborne preservatives shall be re-dried before use. 4.2.2.2 Type WCCA Type WCCA preservatives consist of a mixture of inorganic compounds that undergo chemical changes in the

timber, becoming insoluble and leach resistant. Properties of preservatives of this type include the following: a) the preservatives are suitable for interior and exterior use

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b) the preservatives are non-flammable;

c) the preservatives cause corrosion of certain metals, but treated timber, after a fixation period of 7

days, is generally not corrosive;

d) after having been re-dried timber treated with these preservatives is odorless and clean and,

although slightly coloured, can be painted and glued;

e) wetting and subsequent re-drying during treatment with these preservatives can cause grain raising and

changes in the dimensions and the shape of the timber;

f) the strength properties of a piece of timber are reduced as a result of the timber having been wetted during treatment with these preservatives; the normal working stresses assigned to a specific grade are, however, not affected, although the use of wet timber in a load-bearing application can lead to excessive deflection because of creep; g) after having been re-dried (see 4.2.2.1), timber treated with these preservatives is more susceptible to damage by fire, because of afterglow, than is timber treated with a class C preservative; and h) when timber that has been treated with these preservatives is machined, faster blunting of tools could be

experienced compared to untreated timber. 4.2.2.3 Type WB Type WB preservatives consist of a water-soluble inorganic borate such as disodium octaborate tetra hydrate

or a mixture of borax and boric acid. Timber treatment using preservatives of this type can be carried out

using a diffusion or a pressure process. Diffusion has to be carried out on green timber (ideally, wet off saw)

that has a moisture content of at least 400 g/kg at or near the timber surface and an average moisture content

of at least 600 g/kg. When the pressure process is used, seasoned timber has to be used. The pressure-

diffusion process (i.e. a combination of the pressure and diffusion processes) can be used for the treatment of

green or semi-seasoned timber with borate preservatives. Properties of preservatives of this type include the

following:

a) the preservatives have a low mammalian toxicity;

b) the preservatives are non-corrosive;

c) the preservatives have a wide-spectrum activity against fungi and insects;

d) the timber colour is unaffected after treatment;

e) the preservatives are odourless;

f) wetting and subsequent re-drying during treatment with these preservatives can cause grain raising and

changes in the dimensions and the shape of the timber;

g) the strength properties of a piece of timber are reduced as a result of the timber having been wetted during

treatment with these preservatives; the normal working stresses assigned to a specific grade are, however,

not affected, although the use of wet timber in a load-bearing application can lead to excessive deflection

because of creep; and

h) owing to the water solubility of borates, these preservatives are only suitable for timber for interior use,

unless combined with an appropriate water-repellent system that can provide long term protection against

leaching when used in exterior above-ground H3 conditions.

4.2.2.4 Type WCuAz Type WCuAz preservatives consist of mixtures of copper and azole biocides. Properties of preservatives of this type include the following: a) the preservatives are suitable for interior and exterior use (see clause 11), with the exception of marine

applications;


b) the preservatives are non-flammable;

c) the preservatives cause corrosion of yellow metals, but treated timber, after a fixation period of 2 days, is

generally non-corrosive;

d) after having been re-dried, timber treated with these preservatives is odorless and clean, and although

slightly coloured, can be painted and glued;

e) wetting and subsequent re-drying during treatment with these preservatives can cause grain raising and

changes in the dimensions and shape of the timber;

f) the strength properties of a piece of timber are reduced as a result of the timber having been

wetted during treatment with these preservatives; the normal working stresses assigned to a specific grade

are, however, not affected, although the use of wet timber in a load-bearing application can lead to excessive

deflection because of creep; and

g) after having been re-dried (see 4.2.2.1), timber treated with these preservatives is more susceptible to

damage by fire, because of afterglow, than is timber treated with a class C preservative.

4.2.3 Class O: solutions of organic compound(s) in organic solvents 4.2.3.1 Types OTBTOL, OTBTNP and OZP The active agent commonly used in OTBTOL is tributyltin oxide-lindane; in the case of OTBTNP it is tributyltin napthenate-permethrin, and in the case of OZP it is azole-permethrin. 1 Properties of preservatives of these types include the following: a) the preservatives are more resistant to leaching than are preservatives of type OB, but can be subject to

loss by evaporation; they are suitable for timber for interior use (see 5(e));

b) the preservatives are usually non-staining and non-corrosive;

c) when the solvents have dried off after treatment, timber treated with these preservatives can usually be

painted and glued satisfactorily;

d) the preservatives do not cause any raising of the grain or swelling of the timber and can therefore be used

on machined timber without causing movement or distortion;

e) where foodstuffs are to be located near to timber treated with these preservatives, special precautions

could be necessary to avoid contamination of the foodstuffs; and

f) the solvents are readily flammable and, until the solvents have evaporated, care should be taken with timber

treated with these preservatives.

4.2.3.2 Type OB Type OB preservatives consist of a volatile organic borate (tri methyl borate) that is applied to the timber,

under vacuum, in the gas phase. The active ingredient in this compound is boric acid, which is common to the

WB type preservatives. Properties of preservatives of this type include the following:

a) the preservatives have a low mammalian toxicity;

b) the preservatives are non-corrosive;

c) the preservatives have a wide-spectrum activity against fungi and insects;

d) the timber colour is unaffected after treatment;

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e) at the end of the treatment, the timber is clean and dry, and ready for immediate use; and

f) owing to the water solubility of borates, these preservatives are only suitable for timber for interior

use, unless combined with an appropriate water-repellent system that can provide long term

protection against leaching when used in exterior above-ground H3 conditions.

4.2.3.3 Type OI-D Type OI-D preservatives consist essentially of deltamethrin dissolved in an acceptable solvent. eltamethrin is a single-purpose preservative that provides protection against insects only. If protection is also needed against attack by fungi, a broad-spectrum preservative should be used. Properties of preservatives of this type are as given in 4.2.3.1, and the following: a) the preservative is only suitable for mouldings, ceilings, floorboards and joinery; and b) the preservative is usually non-corrosive, although tests have shown that the corrosion effect of type OI-D preservative on mild steel and galvanized steel fittings becomes more severe with increase in retention.

4.2.3.4 Organic solvents The solvent used with a class O preservative shall be as recommended by the preservative manufacturer, but should preferably be a volatile solvent. Where relevant, it may contain the following additives: a) acceptable colour pigmentation for indicative or decorative purposes; and b) an acceptable waxy oil to control excessive moisture content fluctuations. NOTE 1 A solvent may consist of one or more components. NOTE 2 Certain timber preservatives, for example lindane, are not soluble in aliphatic solvents. 5 Classification of hazard conditions for timber For the purposes of determining the level of preservative treatment required to ensure an acceptable service life of timber, the hazard conditions under which timber is normally exposed to attack by timber-destroying agents are classified as follows: NOTE See clause 11 for specific applications and specific hazards.

a) hazard class H6 (timber in sea water): timber constantly or periodically in contact with estuarine or sea

water and therefore subject to marine borer attack;

b) hazard class H5 (timber in fresh water): timber constantly or periodically in contact with fresh water or

heavy wet soils;

c) hazard class H4 (timber in ground contact): timber, interior or exterior, in direct or indirect

contact with the ground;

d) hazard class H3 (exterior timber above ground): timber not in direct contact with the ground but that will

be exposed to leaching and weathering;

e) hazard class H2 (interior timber above ground): timber used under a roof, not in contact with the ground,

and that will not be exposed to weathering and leaching;

f) hazard class H0-i (single-purpose insecticides, specific end uses): interior timber used for moldings,

ceilings, floorboards and joinery exposed to insect (excluding termites) attack only; and

g) hazard class H0-it (single-purpose insecticides, specific end uses): interior timber used for moldings,

ceilings, floorboards and joinery exposed to insect (including termites) attack only.


6 Preparation of timber for treatment

6.1 General

Before treatment, timber should be selected with regard to its physical properties. The recommendations given in 6.2 to 6.7 (inclusive) should be carefully followed if optimum results from a treatment process are to be achieved. (See also 8.2.) To achieve the recommended penetration of preservatives, adequate sapwood depth is required. Do not preservative-treat timber that contains inadequately cured glue lines. Timber that contains glue lines shall not be treated with a class W preservative,

6.2 Sorting

6.2.1 Species

Ensure that the timber treated in one charge has similar receptivity to treatment (see annex A) and is of the

same species. In the case of the Pinus genus, however, the timber does not have to be of the same species. Do not mix hardwood and softwood species in a charge, except when the weighbridge method for retention determination is being used and when it is permitted in the relevant product specification.

6.2.2 Dimensions

Unless the weighbridge method for retention determination is being used, ensure that the timber treated in one charge is similar in form and dimensions, especially with regard to thickness. When mixing of dimensions is unavoidable, treat to at least the average net retention given in table 3 for the largest dimension in the charge. NOTE In the context of this sub clause, each load in a charge may be considered as a separate charge if the treatment schedule applied is that for the largest dimension of the timber that is most difficult to treat in any of the loads and if the average net retention of each load

is determined.

6.2.3 Timber defects

Only treat timber that is free from decay, resinous patches, gum veins (other than veins that occur below the required minimum depth of penetration), and from splitting that is more than that specified in the relevant

product specification or by the purchaser.

6.3 Seasoning

6.3.1 General

Except in the case of timber to be treated by the diffusion process timber should be seasoned before

preservative treatment.

6.3.2 Moisture content

6.3.2.1 Timber to be treated by the pressure process

The OR average moisture content of timber, determined in accordance with the appropriate of DUS 2014, DUS 2015,DUS 2016 immediately before preservative treatment, shall be as required in the relevant product specification.

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In the case of timber products where drying defects such as warp and splitting are critical, it is recommended that the average moisture content should not exceed 170 g/kg for class O preservatives and 280 g/kg for class C and class W preservatives.

NOTE 1 Timber at these moisture contents, although satisfactory for treatment, should not necessarily be considered as

being properly seasoned timber. NOTE 2 The moisture content of timber treated using the gas phase process is dependent upon timber species and

dimensions, but will not normally exceed 100 g/kg. Correct moisture content should be as recommended by the

preservative manufacturer.

6.3.2.2 Timber to be treated by the diffusion process

Timber to be treated by diffusion should be freshly felled or wet off saw (

6.3.2.3 Timber to be treated by the pressure-diffusion process

No specific requirement is applicable in terms of moisture content of timber to be treated by pressure-diffusion

with diffusible preservatives of type WB, provided that the requirements for penetration and retention are met. NOTE Individual pieces of timber to be treated in the same charge should be of similar average moisture content. The

moisture content of individual pieces should not vary by more than 100 g/kg from the average moisture content of the charge.

6.3.3 Prevention of insect attack during seasoning

Because the sapwood of hardwoods is generally susceptible to insect attack, untreated hardwoods should be protected during seasoning and storage by the application of a suitable timber protectant.

6.3.4 Prevention of mould attack

Superficial mould tends to develop during seasoning before preservative treatment, as well as during the closed-stacked phase following preservative treatment of timber with borates by using the diffusion process. A mouldicide should be applied to the timber during seasoning to prevent this, or alternatively a mouldicide can be added to the borate solution.

6.4 Surface preparation

Only treat timber that is free from precipitated water, dirt and other contaminating substances, and free from rot and insect attack. Remove any outer and inner bark that can inhibit penetration. Remove the bark by peeling or, where minor quantities of surface resin are present, by charring, in both cases removing as little of the sapwood as possible. Patches of impenetrable resin or gum scars or pockets may, depending on the type of timber product, be drilled or pierced to improve penetration of the preservative. Use a centre-to-centre

spacing of at least 25 mm between holes, which should not exceed 3 mm in diameter and 10 mm in depth.

6.5 Shaping

Whenever practicable, perform all shaping and drilling before preservative treatment

6.6 Incising

6.6.1 General

Incising is permissible when this has been agreed upon between the treater and the purchaser of the treated timber. Incising improves penetration in timber that is difficult to treat and reduces the size of surface checks. Do not incise timber of nominal thickness less than 75 mm or faces of softwoods that will be horizontal in use.


6.6.2 Methods

Always make incisions approximately parallel to the general grain direction and to a depth equal to that of the desired penetration (unless this adversely affects the strength of the timber). Space incisions approximately 25 mm apart in rows that are at an angle to the general grain direction and that are approximately 60 mm apart and are such that incisions on the grain direction line are spaced as far apart as possible. Achieve

spacing such that the number of incisions is approximately 650 per square metre.

6.7 Stacking

So stack timber in the treatment tank or cylinder that the preservative liquid has free access to all faces of each piece (except in the case of sawn softwood timber, which can be treated as strapped packages or bundles). Do not treat a unit or an assembly of units in its wrapping or packing. Where relevant, ensure correct positioning of the samples for average net retention determination. NOTE When planed timber is treated with a class O preservative, sticks or laths should be used to separate each layer

from the other.

7 Preparation and control of preservative mixtures

7.1 General

Ensure that a preservative complies with the requirements of the relevant national standard given in table 1.

7.2 Mass concentration

In the case of class W and class O preservatives, use a preservative solution that has a mass concentration such as to ensure that the appropriate requirements for average net retention and minimum preservative penetration given in table 3 are met. However, in no case may the mass concentration of type WCCA solutions be less than 20 g/L and, where an average net retention for type WCCA solutions of at least 16.0 kg/m3 is required, use a solution that has a mass concentration of at least 40 g/L, except in the case of hazard

class H6, where a mass concentration of at least 60 g/L might have to be used. NOTE 1 At low levels of mass concentration, high retentions can be difficult to achieve.

NOTE 2 At no time should the temperature of a type WCCA solution or the temperature of timber immediately before

treatment with such a solution exceed 40 °C.

7.3 Toxicity and safety

All timber preservatives are pesticides and should therefore be handled, mixed and used with care, the manufacturer's instructions being followed where relevant. (See also clause 9.) Avoid bodily contact and ingestion and take appropriate precautions when mixing or using preservatives.

7.4 Flammability

Volatile solvents used in class O preservatives are flammable. Care is therefore necessary when class O preservatives are in storage and when they are used in confined spaces. Exercise care to exclude water (e.g. rain) when a class C preservative is being used in the open tank process, since the mixing of water with such

a preservative can, because of frothing and spilling over, result in a fire hazard.

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8 Application methods for preservatives

8.1 Surface application

8.1.1 Surface brushing and spraying

Surface brushing and spraying methods are useful when the timber has to be treated in situ, and good results

can be obtained on the sapwood of softwood timbers when a class O preservative in a solvent that has good

penetrating properties is used. Brushing and spraying by hand are less effective than other application

methods because coverage might be incomplete or absorbent areas of the timber (such as sapwood) might

not be given the chance to absorb as much as they would if immersed.

8.1.2 Immersion, steeping, deluging

8.1.2.1 General

The penetration and retention achieved by immersion, steeping and deluging are much less than those

obtained by the treatment processes prescribed in 8.2, and may only be used in the case of class O

preservatives used on softwood timber.

8.1.2.2 Immersion

Immersion is potentially a better method than surface brushing or spraying because it ensures that all surfaces of the timber are covered and are able to absorb the preservative. With short periods of

immersion (of a few minutes' duration only), low absorption and penetration are obtained. 8.1.2.3 Steeping Steeping is a somewhat better treatment than immersion. Steeping is immersion for longer periods (hours or

even days), but this is usually not practical. 8.1.2.4 Deluging Deluging is a form of immersion in which individual pieces of timber are passed through a machine where they are sprayed with preservative for a few seconds. Often the timber is passed through an enclosed tunnel in

which the timber is heavily deluged with preservative from a ring of jets although it is not actually immersed.

8.2 Prescribed timber-preservative treatment processes

8.2.1 General

To be classified as a timber-preservative treatment, one of the preservative treatment processes shall be

used, and the required equipment, as given in 8.3 for each process, shall be available at the treatment plant.

8.2.2 Diffusion

The diffusion process is used to treat unseasoned timber. The timber is pressure impregnated with, sprayed

with or immersed in a solution of class W, type WB preservative. In the case of non-pressure application

methods, i.e. immersion or spraying, care should be taken to ensure that all timber surfaces are adequately

wetted. After having been wetted, the timber is closed-stacked under cover for several weeks, to allow the

preservative to diffuse through the timber. During this period, the timber has to be kept covered to prevent any

appreciable drying, since drying will retard diffusion.

The rate of diffusion depends on the moisture content of the timber, and becomes slower as the moisture

content is reduced. Diffusion is the result of the slow movement of the preservative molecules through the


water in the timber; hence only preservatives that are soluble in water, and remain so for several weeks while

in contact with the timber, are suitable for application by this method. The only preservatives recommended

for this application are of type WB. Elevated temperatures will speed up the process.

In the case of pressure impregnation, it is important to obtain the required retention during the treatment

process. The mass concentration of the preservative solution should be adjusted in accordance with the

absorption obtained in timber of varying moisture content. Further penetration of the preservative can be

achieved by stacking the freshly treated timber under cover for a period of time. The same diffusion principles

apply as described above.

8.2.3 Gas phase process

The gas phase process involves enclosing timber in a treatment vessel and drawing a vacuum. A volatile

preservative, organic borate (trimethyl borate) (the only preservative recommended for this process is type

OB), is then injected into the treatment vessel. The liquid vaporizes under vacuum. The resulting gas

penetrates the timber and reacts with timber moisture to form boric acid, which is equivalent to the active

ingredient of type WB timber preservatives. A final vacuum is drawn at the end of the reaction, to withdraw

any surplus gas. The treated timber is clean, dry and ready for immediate use.

8.2.4 Hot or cold open tank process

The hot or cold open tank process will give effective protection to permeable timbers and to sapwood, but is

not recommended for timbers resistant to penetration, for which a high-pressure process (see 8.2.5) is

recommended. Only class C preservatives are commonly applied by the hot or cold open tank process. The

timber is submerged in a tank of preservative which is heated for a few hours. Then either the preservative is

allowed to cool while the timber is still submerged or the timber is transferred to a separate tank of cold

preservative. The heating and cooling periods will vary with the dimensions and species of timber, the type of

preservative and the efficiency of the heating and cooling systems.

8.2.5 High-pressure processes 8.2.5.1 General Treatment under pressure is the most effective way of applying a preservative to timber but in the case of

some resistant timbers, a high pressure can cause collapse, especially when creosote at a high temperature

is used. When such timbers are treated with a class C preservative, it is advisable to use a high temperature

and a moderate pressure. The basic process consists of enclosing the timber in a treatment vessel (usually a

cylinder) and forcing the preservative into the timber under hydraulic pressure. This pressure is maintained

until the required absorption is attained

The pressure may be preceded by a period under vacuum (as in the Bethell (full-cell) process) or under air

pressure (as in the Rueping (empty-cell) process). When no preliminary vacuum or pressure is applied, the

process is known as the Lowry (empty-cell) process. After the pressure cycle, the vessel is drained; a vacuum

is then sometimes applied to adjust the preservative absorption and to "dry" the surface of the treated timber.

The term "empty-cell" is used because surplus preservative is removed by the expansion of air compressed in

the cell spaces while sufficient preservative is left in or on the cell walls to give adequate protection. The term

"full-cell" is used because the cell spaces are also filled or partially filled with preservative

Bleeding of class C preservatives is less likely to occur after an empty-cell process than after a full cell

process. Empty-cell processes allow the achievement of deep penetration and the required net retention.

DUS 2021:2019


Furthermore, when an empty-cell process is used, there is usually less variation in net retention in individual

pieces of timber in a charge.

Pressure processes in general can force preservatives deep into timber and achieve high retentions. They are

widely used to apply class C and type WCCA and WCuAz preservatives to timber, and can also be employed

with type WB preservatives.

8.2.5.2 Bethell (full-cell) process Charge the treatment vessel with timber, seal the treatment vessel, apply a vacuum and maintain the vacuum

for an adequate period. Without increasing the pressure, introduce the preservative at an appropriate

temperature to achieve the requirements given in table 3. Allow the cylinder to fill to capacity, apply a

hydraulic pressure and maintain this pressure until the required absorption is attained. Release the

pressure. Pump the surplus preservative from the treatment vessel and, optionally, apply a final vacuum and

maintain this vacuum for an appropriate period in order to "dry" the surface of the timber.

8.2.5.3 Rueping (empty-cell) process Charge the treatment vessel with timber, seal the treatment vessel, pump air into the cylinder until a suitable

pressure is attained, and maintain this pressure for an adequate period. Then pump the preservative, at its

required temperature, into the treatment vessel at the same pressure. During this period, the preservative

displaces the air into an equalizing (Rueping) tank, except that in the absence of such a tank, the air is

allowed to escape from the treatment vessel at such a rate that the pressure in the treatment vessel remains

constant.

When the treatment vessel has been filled with preservative, raise the pressure by forcing in additional

preservative, and maintain this pressure until the gross absorption is sufficient to comply with the

requirements given in table 3. When the required gross absorption has been reached, release the pressure

and drain the preservative from the treatment vessel. During this period, the compressed air in the timber

expands and drives out some of the preservative. Finally, apply a vacuum and maintain it until the surplus

preservative has been removed from the timber. The amount of preservative remaining in the timber at the

end of the treatment is the net retention (see table 3), as distinct from the gross absorption, which is the

amount contained in the timber at the end of the pressure period.

8.2.5.4 Lowry (empty-cell) process This process is similar to the Rueping process, except that preservative is pumped into the treatment vessel

without any raising of the air pressure in the vessel. Compression of the natural air in the cell spaces in the

timber by the preservative helps to expel the excess preservative on release of pressure.

8.2.6 Low-pressure process

The low-pressure process is carried out at ambient temperature, usually by the Lowry process, with the use of

pressure but without the application of an initial or a final vacuum. Charge the treatment vessel with timber,

seal the treatment vessel, fill it with preservative and then introduce additional preservative until the required

pressure is reached. Maintain this pressure until the desired absorption is attained. Release the pressure and

drain the preservative from the treatment vessel. Because a final vacuum is not usually applied in this

process, surfaces of items treated by the low pressure process are normally not "dry" immediately after

treatment.

This process is only suitable for the application of class O preservatives to finished products such as floor

blocks, flooring strips, door and window frames and other products of normal structural sizes, and then only

provided that the required net retention and penetration (see table 3) are attained. The advantage of this

process is that it can be carried out with the use of light equipment.


8.2.7 The vacuum impregnation (double vacuum) process

The vacuum impregnation process consists of enclosing timber in a treatment vessel and subjecting it to a vacuum. The treatment vessel is flooded with preservative while still under reduced pressure and, when air is admitted, the increased pressure (either atmospheric or slightly above atmospheric) forces the preservative into the timber.

After an appropriate period, the treatment vessel is drained. A final vacuum is commonly used to enable the

preservative absorption to be adjusted and to impart a "dry" surface to the treated timber. The penetration is

somewhat less than that achieved by the high-pressure processes. This process is normally only used for the

application of class O preservatives to softwood.

8.3 Equipment required

At least the minimum required equipment, as given in columns 2 to 8 of table 2, for each timber preservative

treatment process, shall be available at the treatment plant.

Table 2 — Minimum equipment required

1 2 3 4 5 6 7 8

Permissible treatment processes

Equipment Diffusion Hot or

cold open

tank

High-pressure processes Low

pressure

process

Double

vacuum

process

DUS 2015 DUS 2017 DUS 1722

Data recorder on

treatment vessel

–

–

x

x

x

–

–

Thermometer a in

treatment vessel

X

X

X

X

X

X

X

Vacuum gauge b on

vacuum chest or line

– – X X X X X

Pressure gauge on

treatment vessel

– – X X X X –

Retention

determination

Method c

X X X X X X X

Electric moisture

meterd (DUS 2016)

X X X X X X X

Air oven (2014 – DUS 1722

–

–

X

–

–

Increment borer

X

X

X

X

X

X

X

Reagent and relevant

apparatus

X

X

X

X

X

X

X

Diameter tape DUS 1722

X

X

X

X

X

Strength tester DUS 1722 – – X – X

NOTE A dash (–) means “not applicable”.

a Of capacity 0 °C to 100 °C with a 1 °C accuracy. Thermometers are not required when cold preservatives are used. b The pressure vessel and vacuum chest shall have separate pressure and vacuum gauges, and they shall have a minimum diameter size of 100 mm with at least a resolution of 20 kPa. The pressure gauge on the pressure vessel shall be a compound pressure vacuum gauge.

c Use one of the retention methods as given in DUS 2013, DUS 2018 or ,DUS 2019.

d Electric resistance type only.

DUS 2021:2019


e As required for relevant preservative type.

9 Handling and safety of preservative-treated timber

To prevent damage to treated timber, pointed tools should only be used on the ends of treated piles, poles

and sleepers.

Timber treated with a class W preservative becomes wet during treatment and, to prevent distortion, care

should be taken when the timber is stacked for re-drying. As the mass of the timber is substantially increased

by treatment, freshly treated timber should be handled carefully to avoid breakages. Preferably do not apply

metal fittings (excluding anti-split plates and metal markers) to timber treated with type WCCA and WCuAz

preservatives, until the period of fixation (see 9.3) is complete and preferably not until the timber is dry.

In the case of timber treated with WCuAz, the fixation is less temperature dependent than for WCCA. After

impregnation with WCuAz preservative, the freshly treated timber should be protected from rainfall and direct

sunlight until the surface is dry, especially for high retention end uses, and before dispatch. This usually takes

48 h.

In the case of creosoted timber, prevent excessive migration of preservative by using the timber as soon as

possible after treatment, subject to its attaining the equilibrium moisture content of the area in which it is used.

It is recommended that creosoted timber that has to be stored for long periods be rotated (axially) through

180° once every six months, or be protected from direct sunlight, or both.

9.2 Safety

When handling timber after treatment, wear protective gloves if the timber is still wet or contains solvent. No

special precautions are necessary in handling treated timber once the timber has dried, but carry out the

normal practice of washing hands before handling food and before smoking. As timber treated with creosote

does not dry out in the same way as timber treated with waterborne or volatile-solvent-borne preservatives,

continue taking precautions if the surface of the timber remains oily.

Restrict machining of treated timber to a minimum, since machining removes some of the treated layer.

However, if it is necessary to machine or to sand timber that has been treated, use an efficient dust extraction

system.

9.3 Fixation of WCCA preservatives

Due to the toxicity of hexavalent chromium, freshly treated timber should not be dispatched before fixation of

WCCA preservative has been reached. The fixation of WCCA preservatives is very dependent on time versus

temperature (see annex B), and freshly treated timber should be stacked for a period of time until the fixation

is complete before dispatch. Fixation is assumed to be complete when the conversion from chromium VI to

chromium III is achieved.

9.4 Disposal

When treated timber is disposed of it shall be done as specified in the relevant material safety data sheets

(MSDSs)2) of the preservative chemical used to treat the timber.

9.5 Flammability

After the solvent has evaporated, timber treated with a class O preservative is no more flammable than

untreated timber. Provided that the surface of timber has no free creosote (as after a few months' drying or


weathering), creosoted timber presents no greater fire hazard than ordinary timber. Timber treated with a type

WCCA preservative is subject to afterglow.

9.6 Safety handling information labelling

It is recommended that each piece of preservative-treated timber (e.g. poles), or in the case of a package of

units or a bundle of pieces (e.g. laths, brandering and battens), each package or bundle, should have a label

attached to the piece, package or bundle bearing the following minimum safety handling information:

a) caution never to burn treated timber;

b) instruction to wear overalls, a dust mask, goggles and gloves when working with treated timber;

c) to dispose of any treated timber waste to a suitable waste disposal site or landfill; and

d) a reference to where a complete safety information sheet for handling and using preservative treated

timber can be viewed or obtained.

The safety handling information may also be printed on the documentation accompanying every lot, batch,

package, bundle or piece of preservative-treated timber (e.g. sales invoice).

10 Penetration and net retention

The appropriate minimum penetrations and net retentions that have to be obtained to ensure satisfactory

service of timber exposed to specific conditions (see clause 5) are given in table 3.

Table 3 — Requirements for preservative-treated timber

1 2 3 4 5 6 7 8

Hazard

class

Exposure

class

Timber application End use Preservativ

e

type

Average net

Retention

(assay

zone)a

mass fraction

Average net

Retention

kg/m3

Minimum

preservative

penetration

(assay zone)

mm

Soft

wood

Hardw

ood

Soft

woodc

Hardw

oodd

Soft

wood

Har

dwo

od

H6 Marine Timber constantly

or

periodically in

contact with

estuarine or sea

water, and subject

to

marine borer

attack

Poles: pilinge; retaining

walls;

slipways; groynes;

jetties; walkways

WCCA

plus

Creosote

–

_

–

_

24

plus

200

24

plus

200

50 50

Sawn timberf: pilingg;

retaining

walls; slipways; groynes;

jetties;

walkways

WCCA

plus

Creosote

–

_

–

_

24

plus

200

24

plus

200

Compl

ete

sapwo

odh

Co

mpl

ete

sap

woo

d

Poles: agricultural poles;

poles

under flood irrigation;

bridges;

pilinge; groynes;

walkways;

slipways; jetties;

WCCA

plus

Creosote

–

0.76

_

–

0.83

_

16

or

4

or

130

16

or

5,4

or

130

25 20

DUS 2021:2019


agricultural poles

for livestock

pens/retaining wallse

H5 Fresh water Timber constantly

or

periodically in

contact with fresh

water or heavy

wet

soils

Sawn

timberf

Pilingg;

slipways;

groynes;

jetties;

walkways;

retaining

walls; culverts;

flood

gates; drains

WCCA

or

WCuAz

or

Creosote

–

0.76

_

–

_

16

or

4

or

130

16

or

–

or

130

Compl

ete

sapwo

odh

Co

mpl

ete

sap

woo

d

Industrial

cooling

towersi

WCCA

–

–

30 30 Compl

ete

sapwo

od

Co

mpl

ete

sap

woo

d

H4 Ground

contact

Timber in direct

contact with the

ground

Poles Distribution WCCA

or

WCuAz

or

Creosote

–

0.76

_

–

0.83

_

16

or

4

or

115

16

or

5,4

or

115

30 15

Telephone

and street

light

WCCA

or

WCuAz

or

Creosote

–

0.76

_

–

0.83

_

16

or

4

or

115

16

or

5,4

or

115

25 15


1 2 3 4 5 6 7 8

Hazard

class

Exposure

class

Timber

application

End use Preservative

type

Average net

Retention

(assay

zone)a

mass fraction

Average net

Retention

kg/m3

Minimum preservative

penetration

(assay zone)

mm

H4

(continued

Agricultural poles;

landscaping structures;

playground structures;

building; fencing;

pergolas; carports;

flower boxes; vine and

orchard trellises

WCCA

or

WCuAz

or

Creosote

Soft

wood

Hard

wood

Soft

woodc

Hard

woodc 20 13

–

0,42

–

–

0,5

–

12

or

2,5

or

100

12

or

3,3

or

100

Complete

sapwood

Complete

sapwood

Posts (guard-rail)

Piling; agricultural poles for livestock pens

See hazard class H5

Sawn

timberf

(and

specified

roundwood

products)

Sawn rectangular

posts; landscaping

structures; playground

structures; building;

fencing; pergolas;

carports; flower boxes;

decking; bridges

WCCA

or

WCuAz

or

Creosote

–

0,42

–

–

–

–

12

or

2,5

or

100

12

or

2,5

or

100

Complete

sapwoodh

Complete

sapwood

Complete

sapwoodh

or 20

Complete

sapwood

or 13

Rail bearers

20 13

General purpose poles

Stakes; garden edging

Sawn

WCCA or WCuAz or Creosote

– 0,42 –

– – –

6 or 2,5 or 80

Complete sapwood

Complete sapwood

DUS 2021:2019



1 2 3 4 5 6 7 8

Hazard class

Exposure class

Timber application

End use Preservative type

Average net Retention (assay zone)a mass fraction

Average net Retention kg/m3

Minimum preservative penetration (assay zone) mm

Soft wood

Hardwood

Soft woodc

Hardwoodd

Soft wood

Hardwood

H4 (continued

Round


– 0,42 –

– 0,50 –

6 or 2,5 or 80

6 or 3,3 or 80

5 5

Piling See hazard class H5

H3 Exterior above ground

Timber not in contact with the ground but exposed to leaching and weathering

Poles Cross-arms and spacers


– 0,42 –

– 0,50 –

6 or 2,5 or 80

6 or 3,3 or 80

20 15

Landscaping structures; playground structures; building; fencing rails; pergolas; carports; vine trellis


– 0,23 –

– 0,23 –

8 or 1,4 or 80

8 or 1,5 or 80

20 13

Round droppers 10 10

Spacer blocksj WCCA or WCuAz or Creosote

– 0,23 –

– – –

8 or 1,4 or 80

8 or – or 80

Complete sapwood

Complete sapwood

Sawn timberk

(and specified roundwood products)

Balustrades; fencing bearers and slats; outdoor decking and beams; garden furniture; laminated beams; weather board; steps; cladding; stairs; gates; fascia boards; plywood; sawn droppersl; slabbed poles; cylindrical rails; halfroundsm


– 0,23 –

– – –

8 or 1,4 or 80

8 or – or 80

Complete sapwood

Complete sapwood

DUS 2021:2019


1 2 3 4 5 6 7 8 Hazard class

Exposure class

Timber application





Soft wood

Hardwood

Soft woodc

Hardwoodd

Soft wood

Hardwood

H3 (concluded)

internal Timber used under a roof, not in contact with the ground, and that will not be exposed to leaching and weathering

General purpose poles; machined polesn

for log homes


– 0,42 –

– 0,50 –

6 or 2,5 or 80

6 or 3,3 or 80

5 5

Laths

Poles:

Building structures; roof trusses

WCCA or WCuAz or Creosote or TBTOL or TBTNP or Borate (boric acid equivalent)

– 0,23 – – – –

– 0,23 – – – –

or 1,2 or 80 or 1 or 1,3 or 5

8 or 1,5 or 80 or 1 or 1,3 or

Sawn timberk:

(and specified roundwood products)

Laminated beams; roof trusses; structural timber; ceiling boards; flooring; panelling; doors; cupboards; skirting; window frames; plywood; slabbed poles; cylindrical rails; half-roundsm

WCCA or WCuAz or Creosote or TBTOL or TBTNP or ZP or Borate (boric acid equivalent)

– 0,23 – – – – –

– – – – – – –

6 or 1,4 or 80 or 1 or 1,3 or 0,40 or 5

6 or – or 80 or 1 or 1,3 or 0,40 or 5

Complete sapwood

Complete sapwood


1 2 3 4 5 6 7 8 Hazard class

Exposure class

Timber application





Soft wood

Hardwood

Soft woodc

Hardwoodd

Soft wood

Hardwood

H2 (concluded

General purpose poles; machined polesn for log homes

WCCA or WCuAz or Creosote or TBTOL or TBTNP or ZP or Borate (boric acid equivalent)

– 0,23 – – – – –

– – – – – – –

6 or 1,2 or 80 or 1 or 1,3 or 0,40 or 5

6 or – or 80 or 1 or 1,3 or 0,40 or 5

20 13

Laths Deltamethri

-

-

0,003

0,003

5 5

H0-io Dry interior

Timber used under a roof, not in contact with the ground, exposed to insects other than termites, and not exposed to fungal attack or leaching and weathering

Sawn timberk: Mouldings;

ceilings; floorboards; joinery

Complete sapwood

Complete sapwood

DUS 2021:2019


1 2 3 4 5 6 7 8 Hazard class

Exposure class

Timber application End use Preservative type




Soft wood

Hardwood

Soft woodc

Hardwoodd

Soft wood

Hardwood

H0-ito Dry interior

Timber used under a roof, not in contact with the ground, exposed to insects including termites, and not exposed to fungal attack or leaching and weathering

Sawn timberk:

Mouldings; ceilings; floorboards; joi

Deltamethri

- - 0,01 0,01 Complete sapwood

Complete sapwood

NOTE 1 A dash (–) means “not applicable”. NOTE 2 Timber treated with TBTOL, TBTNP, ZP or borate could be used for hazard class H3, provided that it is continuously protected by a suitable well maintained coating

a Average net retention (assay zone) levels expressed in a mass fraction of Cu + biocide. b Timber treated with WCuAz preservatives: If the actual timber density and/or sapwood content are less than those in c) and d), then a suitable sampling plan (see annex C) may be used to determine the actual net retention, using the following formula: ANR = mass fraction (column 6) × oven dry timber density × sapwood content. c In the case of softwoods treated with WCuAz preservatives, the average net retention expressed in kg/m3 (total volume) is calculated by converting from the mass fraction active ingredients using an oven dry timber density of 580 kg/m3, and a sapwood content of 100 % for sawn timber and 90 % for poles. d In the case of hardwoods treated with WCuAz preservatives, the average net retention expressed in kg/m3 (total volume) is calculated by converting from the mass fraction active ingredients using an oven dry timber density of 800 kg/m3, and a sapwood content of 80 % for large poles, and an oven dry density of 650 kg/m3, and a sapwood content of 100 % for laths and small diameter poles. e Due to preservative treatment requirements, all piling and agricultural poles for use in livestock pens or retaining walls that are to be used in direct contact with the ground or that will be constantly or periodically in contact with fresh water or heavy wet soils (or both), shall be treated and marked in accordance with hazard class H5. All piling that will be in contact with estuarine or sea water shall be treated and marked in accordance with hazard class H6. f The only hardwood recommended is species with a permeable heartwood. Sawn eucalyptus species are not suitable for hazard classes H6, H5 and H4. g Preferably in round wood form with complete envelope of sapwood, but if sawn timber is used, a large amount of sapwood shall be present. h If the required retention is to be achieved, a large amount of sapwood shall be present. i Timber selected for 100 % sapwood. j Spacer blocks: Full penetration even with lower retention. k In the case of hardwood species, some sawn timber products (see 12.3) need not be preservative treated due to their low penetrability. l Type WCCA preservatives shall not be used for the treatment of hardwood sawn droppers. m The treatment of half-rounds manufactured from hardwood species with a class W preservative is not recommended. n Machined poles for log homes manufactured from hardwood shall be machined in such a way that the sapwood required for penetration is not disturbed. o The end uses for this hazard class, unlike the other hazard classes, are restricted to those given in column 4 only (see clauses 5(f) and 5(g)). Only products included in column 4 shall be allowed to be treated.


11 Recommendations for the use of timber preservatives in specific applications

11.1 Contact with food

11.1.1 Direct contact with food for human consumption

For applications in which the preservative-treated timber will be in direct contact with food intended for human

consumption, use only a timber preservative of type WB, type WCuAz or type WCCA.

In the case of a type WCCA preservative, do not use the timber within 7 days of treatment and thoroughly

hose the timber down and scrub it or dress it lightly before putting it into use. Such treated timber is known to

have been used satisfactorily in cold storage chambers, bread bakery tunnels, grain storage silos and fishing

boats.

NOTE Direct contact is also considered to exist where water can cause a bridging contact between the preservative-

treated timber and the food.

11.1.2 Direct contact with feeds for livestock

For applications in which preservative-treated timber will be in direct contact with feeds for livestock and

provided that, when the timber is to be used with liquid feeds, the pH value of the feeds is within the range 6,0

to 8,0, use only a timber preservative of type WCCA or type WCuAz.

11.1.3 Indirect contact with food or feeds

For applications in which preservative-treated timber will be in indirect contact with food or feeds, use only a

timber preservative of type WB, type WCuAz or type WCCA. Class C preservatives may be used, provided

that the treated timber is properly coated with an acceptable creosote-compatible sealant.

NOTE 1 Indirect contact is considered to exist in the case of truck or container floors, wooden pallets, etc., used with

packed goods.

11.2 Human contact

For applications in which preservative-treated timber is in direct contact with the human skin, for example in

the case of playground equipment, use only a timber preservative of type WB or type WCuAz. Class C

preservatives and a type WCCA preservative may be used, provided that the treated timber is properly coated

with an acceptable sealant which, in the case of class C preservatives, is creosote-compatible. Timber

preservatives could be hazardous to people with sensitive skins.

11.3 Animal contact

11.3.1 Continuous direct contact

For applications in which preservative-treated timber will be in continuous direct contact with animals (and

bees), use only the following preservatives:

a) for animals: all preservatives other than class C, and preservatives other than class O that contain

pentachlorophenol or its salts; and

DUS 2021:2019


b) for bees: type WCuAz and suitable preservatives of type WB which should be painted or protected by a

suitable water repellent.

NOTE In the case of an organic solvent-borne preservative, the solvent should be allowed to evaporate completely before

the timber is used.

11.3.2 Periodic direct contact

For applications in which preservative-treated timber will be in periodic contact with animals, all classes of

preservatives may be used. Where repeated licking of treated timber by animals can be expected, use a type

WCCA or a type WCuAz preservative. In the case of a creosote-based preservative, use a type and a process

of application such as to minimize bleeding.

11.4 Contact with plants

There are no restrictions on the class of preservative to be used on timber that will be in direct contact with

plants, although damage could appear on plants as a result of direct contact with freshly creosoted timber.

11.5 Combustion gases

Because toxic gases will be released as a result of the combustion of preservative-treated timber, take care to

avoid prolonged exposure to such gases.

11.6 Timber for use in cooling towers

The use of softwood, treated as in (a) to (d) below, is recommended for cooling towers:

a) preservative: use a type WCCA preservative;

b) solution strength: use a solution strength of at least 60 g/L;

c) retention: see table 3; and

d) penetration: see table 3.

12 The use of preservative-treated timber in specific areas in Uganda.

12.1 Qualification

To qualify as being adequate for its purpose, structural timber of the two main species used in a permanent

building in the areas given in 12.2 and 12.3 shall be preservative treated in accordance with 12.4

12.2 Gymnospermae (coniferous species)

Sawn timber (including planed and profiled timber) and poles or logs (round or partly round) of the softwood

species shall be treated in accordance with 12.4 when used in the following municipal

12.3 Angiospermae (broadleaved species

All sawn timber, planed timber, and poles or logs (round or partly round) of the hardwood species shall be

treated in accordance with 12.4 when used within the borders of Uganda, except for the following items:

a) laminated timber;

b) block and strip flooring;


c) ceiling boards;

d) paneling;

e) mouldings and joinery;

f) garden furniture;

g) outdoor decking boards; and

h) non-sapwood-containing, kiln-dried and planed, sawn boards processed from eucalyptus species).

12.4 Preservative treatment

The preservative treatment of timber shall comply with the provisions of us EAS 3226, US EAS 3264, USEAS

3225

13 Treatment plant area compliance

All treated timber shall be treated in a preservative treatment plant that complies with the provisions given in

annex D. The checklist given in annex E shall be used for conformity assessment.

Annex A

(informative)

Permeability of commercial timber species

A.1 Amenable to impregnation

The sapwood of the following timbers can be easily impregnated, the heartwood only sometimes.

SOFTWOODS HARDWOODS.

Pinus canariensis Eucalyptus fastigata

P. caribaea E. fraxinoides

P. elliottii E. grandis

P. patula

P. pinaster

P. roxburghii

P. taeda

A.2 Moderately amenable to impregnation

The sapwood of the following timbers can be fairly easily impregnated, the heartwood rarely.

SOFTWOOD HARDWOODS

Pinus radiata Entandrophragma cylindricum (Sapele)

Eucalyptus citriodora

E. cladocalyx

E. cloeziana

E. diversicolor

E. maculata

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Annex B

(Informative)

WCCA fixation chart

The fixation chart in figure B.1 gives an indication of the time versus timber temperature required for

fixation to be achieved.


Annex C

(Informative)

Sapwood and density calculation for the determination of WCuAz timber-preservative

retentions

C.1 Introduction

This standard includes the option for timber treatment plants to determine preservative retentions

(expressed as kilograms per cubic metre) using a mass fraction retention, the oven dry density of

the treated or assay zone, and the sapwood content of the material being processed.

This sampling method should be used to determine the target retention (kilograms per cubic metre)

of the total timber volume by determining the basic actual oven dry density and sapwood content of

the timber being treated at a given timber treatment plant.

C.2 Materials needed

C.2.1 Determination of basic sapwood content

To determine basic sapwood ratio, 30 or more pieces of timber from the same population as the lot

to be treated is selected at random. If the samples are sawn timber, then no more than 3 pieces

may be selected from the same package of units or bundle of pieces (e.g. brandering, battens and

flooring, and decking boards). The sample can be kept in the stacks or in their bundles, and merely

marked for observation.

C.2.2 Determination of basic density

To determine basic density, 30 or more pieces of timber from the same population as the lot to be

treated are selected at random. The maximum moisture content of the samples shall be as required

in the relevant product specification. The pieces are to consist of 100 % sapwood and be at least

300 mm in length with a minimum mass of 100 g.

C.3 Method

C.3.1 Apparatus

C.3.1.1 Calibrated digital scale, capable of measuring to the nearest 1,0 g.

C.3.1.2 Electric moisture meter, preferably fitted with insulated electrodes and suitable for the

determination of moisture content of timber.

C.3.2 Determination of the basic density (DB)

C.3.2.1 In order to determine the basic density of the timber, the oven dry density (DOD) of each

timber sample in kilograms per cubic metre is determined by using the following formula:

D = M X 0.001 OD MC

1+ 1000 x V

where

M is the mass of the sample, in grams;

MC is the average moisture content of the three measurements per sample, in grams per

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kilogram;

V is the calculated volume of the sample, in cubic metres.

C.3.2.2 The basic density (DB) is determined by using the following formula:

DB = DAVE + SD

where

DB is the basic density, in kilograms per cubic metre;

DAVE is the average oven dry density of all the samples (as determined in C.3.2.1), in

kilograms per cubic metre;

SD is the standard deviation of all the samples, in kilograms per cubic metre.

C.3.3 Determination of the basic sapwood content (SC)

C.3.3.1 In order to determine the basic sapwood content, the sapwood content of each timber

sample is determined by observing the one end of each sample. Before making any observations,

carry out the following procedure:

a) spray the one end of the untreated sample with a heartwood indicator pertinent to the timber

species;

b) measure the average diameter of the sample at the sprayed end (OD); and

c) measure the average diameter of the heartwood portion (HD).

C.3.3.2 Determine the sapwood content of the sample (SCs) as a percentage, as follows:

SCs= OD2 – HD2 X 100

OD2

where

OD is the average overall diameter of the sample, in millimeters;

HD is the average heartwood diameter of the sample, in millimeters.

C.3.3.3 Calculate the basic sapwood content (SC) as a percentage, as follows:

SC = SAVE + SDP

where

SAVE is the average sapwood ratio of all the samples (as determined in C.3.3.2), as a

percentage;

SDP is the standard deviation of all the samples, as a percentage.

C.3.4 Determination of the target average net retention (total timber volume)

Calculate the minimum retention (R) in kilograms per cubic metre, as follows:

R DBX SCX ANR

10 000

where

R is the average net retention, in kilograms of active chemical per cubic metre total volume;

DB is the basic density (as determined in C.3.2.2 above), in kilograms per cubic metre;

SC is the basic sapwood content (as determined in C.3.3.3 above), as a percentage;


ANR is the average net retention as given in column 6 of table 3, as a mass fraction.

NOTE The sampling method should be repeated:

a) at least every three months; or

b) when a new timber supplier is used; or

c) when a different timber species is used to the timber previously sampled

or any combination of (a), (b)

and (c)).

(normative)

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Annex D (Normative)

Treatment plant area conformity requirements

D.1 Occupational hygiene

D.1.1 Emergency facilities

Emergency showers and eyewash facilities shall be installed within the bunded area.

D.1.2 Contaminated water from showers and eyewash facilities

Water from the showers or eyewash facilities that is contaminated with treating solution shall not be

discharged into the ablution drains or storm water drains. In the case of waterborne preservatives,

the contaminated water could be used in the preparation of treating solutions; otherwise it shall be

collected and stored until it can be neutralized and disposed of in an approved way (see D 3)

D.1.3 Eating, drinking and smoking

No eating, drinking or smoking shall be allowed within the treatment area (see D.2.2.10.1) and no

foodstuffs shall be stored within this area.

D.1.4 Rainwater

Provision shall be made to divert all storm water from the treatment area. This diverted water shall

remain uncontaminated. Should there be any signs of contamination, the water shall be contained

and used in the treatment process. (See also D.1.2.)

D.2 Safety

D.2.1 Chemical safety programme

Chemical safety is an important part of an environmental management programme. Significant

elements shall include:

a) monitoring programmes for workers’ health, in order to ensure that exposure limits are adhered

to and that proper records are kept of accidents and incidents involving chemicals

b) appointing a person responsible for monitoring occupational health and safety;

c) using only registered chemicals and keeping all relevant information on handling, storage and

first aid up to date;

d) controls to ensure that correct handling and safety procedures are followed by all employees;

e) information on and training in the above, involving employees (see D.5.1); and

f) ongoing liaison with local emergency services (fire brigade, hospitals, etc.) regarding chemical

safety procedures.

D.2.2 Plant safety

D.2.2.1 Bunded area

D.2.2.1.1 General

All constituent parts of a timber treatment plant shall be within a bunded area. The bunded area may

be either covered or uncovered (see D.2.2.10.3). The walls and floor of the pit or bunded area shall

be of an impervious material and shall be maintained in that condition.


NOTE ideally all bund walls should finish above normal ground level.

D.2.2.1.2 Size

The pit or bunded area shall be of adequate size to accommodate the total volume of the chemicals

present, plus 10 % of the volume. A separate bunded tank farm of adequate size to accommodate

the volume as determined in table D.1 shall be provided for chemicals in storage. (See D.2.4.)

Table D.1 — Total volume of tank farm

1 2

Number of tanks Total volume of tank farm

1 110 % of the volume of the tank

2 100 % of the volume of the largest tank plus 50 % of the volume of the second tank plus 10 % of this calculated volume of the two tanks.

3 100 % of the volume of the largest tank plus 30 % of the volume of the remaining two tanks plus 10 % of this calculated volume of the three tanks

4 100 % of the volume of the largest tank plus 20 % of the volume of the remaining three tanks plus 10 % of this calculated volume of the four tanks.

5 100 % of the volume of the largest tank plus 15 % of the volume of the remaining four tanks plus 10 % of this calculated volume of the five tanks.

6 100 % of the volume of the largest tank plus 12 % of the volume of the remaining five tanks plus 10 % of this calculated volume of the six tanks.

7 or more 100 % of the volume of the largest tank plus 10 % of the volume of the remaining six or more tanks plus 10 % of this calculated volume of the seven or more tanks.

D.2.2.1.3 Position

The location of the door of the treatment vessel relative to the pit or to the bund wall shall be such

that any chemical solution remaining in the treatment vessel spills into the pit (or bunded area).

D.2.2.2 Treatment vessels

D.2.2.2.1 General

If compressed air or liquid pressure is used during the treatment process, the treatment vessel shall

comply with the requirements of the relevant national legislation (see foreword) All treatment

vessels shall be regularly inspected for deterioration, for example corrosion, and immediately

repaired when necessary.

D.2.2.2.2 Seal

Before the door of a treatment vessel is closed, care shall be taken to ensure that the door seal is in

position and has been wiped clean of any debris, and that the seal is in good workable condition.

D.2.2.2.3 Door safety

The door of the treatment vessel shall be closed during non-working hours. A warning notice

indicating that all the chemical solution in the treatment vessel has been pumped out shall be placed

on the door face, even though a reliable mechanical fail-safe interlock system is installed (see

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D.2.2.2.4). Where the door is suspended from a single bolt, a safety chain shall be added in case

the bolt breaks.

NOTE A treatment vessel door that is not fully and safely locked during the treatment process can be dislodged and blown

open either by internal pressure or by the weight of the solution.

D.2.2.2.4 Fail-safe interlock system

Except in the case of multiple-bolt doors, a fail-safe interlock system (mechanical, not electrical) that

will prevent the door of the treatment vessel from being opened during the process cycle shall be

fitted to avoid unnecessary spillage and flooding.

NOTE An example of such a fail-safe interlock system is a valve fitted over the door-opening mechanism, which will

prevent the operator from loosening the bolt direct, in order to open the door. This valve will have to be opened first and all

remaining internal pressure will therefore be relieved.

D.2.2.2.5 Control panel signal

In the case of automated plants, the control panel shall receive an electrical signal indicating when

the door is fully locked.

D.2.2.2.6 Pressure-relief valves

The treatment vessel shall be provided with a pressure-relief valve that prevents the plant from

being operated at pressures exceeding the working pressure of the treatment vessel. An additional

pressure-relief valve shall be provided if the pressure pump is capable of exceeding the test

pressure of the vessel. It shall be set to bypass at a slightly higher pressure (+25 kPa to +50 kPa)

than the first pressure-relief valve, thus acting as an added safety precaution. The valve shall be sealed

to prevent tampering or unnecessary adjustment.

D.2.2.2.7 Vacuum chest If a vacuum chest is linked into the vacuum line, a quick-action valve shall be situated between the treatment vessel and the vacuum chest and shall be kept in the closed position during any pressure cycle. The chest shall be fitted with a sight glass or with a level switch. NOTE When the treatment vessel is full, the solution level will show in the sight glass and the operator can close the valve to stop the vacuum pump from flooding. A level switch will stop the vacuum pump when the treatment vessel is flooded. D.2.2.2.8 Marking Each treatment vessel defined by the relevant national legislation (see foreword) as a pressure vessel shall be legibly and durably marked with at least the following information: a) the design code; b) the working pressure and test pressure; c) the treatment vessel manufacturer's name; d) the drawing number; e) the date of manufacture; f) the date of the hydraulic pressure test, and the test pressure, in megapascals; g) the inspection authority (where applicable); and h) the plant manufacturer's unique identification number. D.2.2.2.9 Rails The rails shall be clear and in good working condition. When the treatment vessel is loaded, the rails shall be aligned and properly secured to prevent derailments. Provision shall also be made to prevent the trolleys from floating off the rails during the treatment process.


D.2.2.3 Tanks D.2.2.3.1 General All tanks manufactured from corrosive materials shall be protected against external corrosion (by means of at least a prime coating and a top coating). Where corrosive chemicals are used, the interior of the tanks shall be coated with a suitable epoxy coating. D.2.2.3.2 Position The tanks shall be placed on a firm foundation within the bunded area. If mild steel tanks are used, they shall be elevated above the ground for air circulation by 50 mm to 100 mm. D.2.2.3.3 Vapours Some chemicals or solvents give off flammable vapours. Smoking shall not be allowed in the treatment plant areas. "No smoking" signs shall be posted. Because vapours can accumulate in a closed tank or above a creosote tank or under a roof, tanks shall be well vented. Special precautions shall be taken when tanks are being cleaned, when samples are being drawn from a creosote tank or when a manhole or door is being opened. The correct safety clothing shall be worn at all times (see D.5.2.7). Smoking areas shall be demarcated. D.2.2.3.4 Maintenance and inspection All closed-up tanks shall be fitted with manholes for maintenance and inspection purposes. Manhole covers shall be secure. The manholes shall be so positioned that they are accessible and, if possible, well ventilated. No individual shall be allowed to enter an enclosed tank without having obtained the necessary authorization by management and without supervision. D.2.2.3.5 Open tanks Open tanks shall be protected with suitable handrails to prevent persons from falling into them.

D.2.2.3.6 Sampling taps All above-ground working tanks (excluding creosote tanks) shall have easily accessible sampling taps that give a representative sample of the contents. Each sampling tap shall be locked or shall have a removable handle. D.2.2.3.7 Marking Each tank shall be legibly and durably marked with at least the following information: a) the total tank capacity, in litres; b) the construction material; c) the wall thickness, in millimeters; d) the type of treatment solution that the tank contains; and e) in addition, in the case of measuring and mixing tanks, the tank capacity, in litres per millimeter of depth. D.2.2.4 Pipe work and valves D.2.2.4.1 Pipe work All pipe work shall be protected against damage and corrosion, and shall be easily accessible for inspection and maintenance. D.2.2.4.2 Valves Valves shall be easily accessible for operation and regular inspection. All valves shall be closely checked for leakages, especially on the vacuum circuit, where air leakage is more difficult to detect. D.2.2.4.3 Tank overflow

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Tanks shall be provided with overflow pipes of suitable diameter to ensure fast drip-free overflow from storage tanks to measuring tanks and from measuring tanks to mixing tanks. These overflow pipes shall form part of a closed-circuit system. D.2.2.5 Water supply To prevent siphoning or back-flow, a water supply pipe shall feed into the top of a tank that forms part of the treatment plant unless fitted with a ball float valve. (See also D.1.2.) D.2.2.6 Mixer (if present) and mixing process D.2.2.6.1 Design The design of a mixer shall be such as to prevent any liquid from being splashed or spilled from the mixing tank. D.2.2.6.2 Mixing process D.2.2.6.2.1 The mixing process shall take place at atmospheric pressure. During the loading of chemicals into the mixing tank, the procedures recommended by the chemical supplier shall be followed. D.2.2.6.2.2 Treatment solutions shall be introduced from the mixing tank into the storage tanks by means of a closed-circuit system. D.2.2.6.2.3 Chemical concentrates in liquid or paste form shall be passed carefully into a dosing vat, from where they will be gradually introduced into the mixing tank. D.2.2.6.2.4 Chemicals in powder form shall be carefully placed into a perforated cage within the mixing tank. From there, they will then be flushed into the solvent in the mixing tank, to provide the working solution required. D.2.2.6.2.5 The mixing process should preferably be done by agitation and not by stirring. If the agitators create rotation of the contents, side baffle fins shall be installed in the mixing tank. NOTE Mixing by means of a high volume transfer pump is very efficient. D.2.2.6.3 Open container Open chemical containers shall not be stored in the mixing area. The chemicals needed for a mix shall be used up or shall be returned to the lock-up storage area. All empty containers and containers with unused chemicals shall also be returned to the lock-up storage area (see also D.2.4). Mixes shall be calculated in full drum or bag multiples, since it is undesirable to have small portions of the concentrated chemicals lying about. D.2.2.6.4 Drum washers A drum washer should be used to empty containers of paste products. High-pressure water jets should be avoided as a means of mixing, owing to the health hazard presented by the mist. D.2.2.7 Pumps D.2.2.7.1 Protective guard All couplings, pumps and motor shafts shall be well protected, to prevent loose clothing from getting caught in them. D.2.2.7.2 Leakage Pumps shall be regularly inspected for leaks. Gland leakage shall be led away to the sump or pit, for recovery into the treatment system.


D.2.2.8 Electrical control panel D.2.2.8.1 Protection All electrical control panels and switches shall be situated under cover, away from rain, chemical spray and spillage. D.2.2.8.2 Labelling All valves, switches, isolators, etc., shall be suitably identified to enable a person to operate the plant after he has read the treatment manual. All functions of the plant shall be recorded step by step in the manual, with all the valve numbers being given. D.2.2.8.3 Electrical installation All electrical installations shall be installed by a qualified competent person and shall be checked at regular intervals to ensure that the equipment is in safe working order. D.2.2.8.4 Flameproof equipment In terms of SANS 60079-1, flameproof motors and fittings shall be used in the case of flammable solutions (including creosote and light organic solvent preservative (LOSP)) and shall be checked and maintained and the results kept on record. D.2.2.9 Haulage or extraction of timber from the treatment vessel Timber handling equipment varies and is generally dependent on local conditions. A forklift or winch is often used. To prevent injuries and downtime, equipment (e.g. winch drum, rope and lifting devices) shall be regularly inspected and checked. The winch shall be protected with an overload switch and a drum guard to prevent cross-winding: in the case of bollard winches, a foot-switch that will allow the operator to stop the winch, and in the case of drum winches, a non-latching dead man's switch. When applicable, crosby clamps shall be fitted correctly. D.2.2.10 Site D.2.2.10.1 Treatment and storage areas The areas for the treatment of timber and for the storage of treated timber shall be clearly demarcated. All practical precautions shall be taken to prevent the environment from becoming contaminated with timber treatment chemicals. D.2.2.10.2 Drip pads D.2.2.10.2.1 Storage drip pad If a treatment process without a final vacuum is used, a storage drip pad shall be provided that is adjacent to the treatment plant and that can accommodate a quantity of timber at least 10 % more than the maximum quantity treated over any 24 h period. The storage drip pad shall have an impervious floor slab that drains back to the pit or bunded area, to contain any drippage or spillage. (See also D.4.1.) D.2.2.10.2.2 Bogie rail drip pad A bogie drip pad, immediately adjacent to the treatment plant and of at least the same length as the treatment vessel, shall be provided at bogie rails and traverses. The drip pad shall have an impervious floor slab that drains back with a minimum fall of 1:500 to the bunded area, to contain any drippage or spillage. The drip pad shall project at least 300 mm on either side of the timber bogies on the rails or traverses. D.2.2.10.3 Cover

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At least one of the following requirements shall be met: a) If the size of the bunded area conforms only to D.2.2.1.2, then a cover is required over at least the bunded area plus over any other drip pads that drain into the bunded area. b) A cover over the bunded area is not required if the bunded area complies with the requirements of D.2.2.1.2 and can accommodate a 1 in 50 year flood over an area that includes the bunded area and any uncovered drip pads that drain into the bunded area. D.2.2.10.4 Housekeeping Housekeeping is of the utmost importance in and around the treatment plant area. All areas that are subject to the build-up of chemical deposits (except oil-borne preservatives and LOSPs) shall be kept clean by regular hosing down with water, which shall be directed into collection sumps for reuse or for suitable disposal. The practice of dry sweeping is not allowed. Oil-borne preservatives and LOSP deposits shall be soaked up with sawdust and shall be disposed of in accordance with D.3. D.2.2.10.5 Stacking Timber shall be stacked safely and neatly to prevent it from falling and causing injuries. The height of a stack shall be not more than three times its base width. D.2.3 Operator’s office or control room D.2.3.1 General There shall be a functional operator’s office or control room at the plant. D.2.3.2 Ergonomics D.2.3.2.1 Lighting To ensure a pleasant working atmosphere, the operator's office should be large enough and have adequate lighting. It should be able to accommodate a suitable sink, shelves for equipment, and a desk, chair and filing cabinet or cupboard. D.2.3.2.2 Ventilation The operator's office shall be well ventilated to remove all vapours. D.2.3.3 Office rules Only the authorized personnel shall be allowed into the office. Only laboratory chemicals and tools used in the treatment process may be kept in the office, neatly stored. Chemical analysis may be done in the office but, after analysis, all the samples shall be returned to the treatment plant. D.2.4 Chemical off-loading and storage area D.2.4.1 Off-loading area All deliveries of chemicals shall be made in a clearly demarcated lockable storage area. This area shall be of sufficient size to accommodate bulk or drum supplies (or both). Care shall be taken to provide adequate safety during the off-loading and storing procedures. Protective clothing shall be worn while the chemicals are being handled. (See also D.5.2.) The off-loading area shall be paved with impervious load-bearing material and shall be so designed that it drains into the bunded area appropriate for the type of chemical being stored. D.2.4.2 Locked storage area Chemicals shall only enter the treatment plant in adequately sealed containers or in tankers. The chemicals shall be kept in a lock-up storage area or tank. A stock book of all chemicals received and mixed shall be kept in accordance with the Quality Management Systems procedures.


D.3 Waste management and disposal D.3.1 Contaminated materials D.3.1.1 Treated timber D.3.1.1.1 Disposal of treated timber waste Treated timber waste shall be disposed of in a suitable and lawful way. Disposal options for timber waste treated with currently used chemicals are given in D.3.1.1.2 and D.3.1.1.3. Treated timber shall not be used for domestic heating, or for cooking or for making charcoal. D.3.1.1.2 Timber treated with copper-chromium-arsenic (CCA) Timber treated with CCA shall be disposed of in an approved landfill. Timber treated with CCA shall not be disposed of by means of burning. D.3.1.1.3 Timber treated with other treatment chemicals Timber treated with other treatment chemicals shall be disposed of in an approved landfill or by burning. Burning shall only be carried out in non-residential areas, and the ash shall be disposed of in an approved landfill. D.3.1.2 Containers and packaging All used containers (drums, plastics bags, etc.) shall be neutralized and rinsed three times and returned to the chemical supplier. If this is not possible, containers shall be neutralized and made unusable by holing and crushing before disposal in a dumping area approved by the local authorities. (Rinsing should be re-used as process water.) NOTE Contaminated waste (drums, containers, plastics bags, etc.) that accumulates on the site should not be disposed of in municipal dumping areas. D.3.1.3 Other contaminated material Contaminated sawdust, sand, etc., shall be disposed of in a dumping area approved for the purpose by the relevant regulatory authority. These waste materials shall not be used for mulching, gardening or any commercial purposes. D.3.2 Chemical sludge Sludge shall be stored in containers that are resistant to acid corrosion as recommended by registered waste disposal companies. These containers shall be stored in a secure bunded area and shall be disposed of by a registered waste disposal company. Chemical sludge shall not be disposed of into sewers or municipal drains. NOTE Chemical sludge is produced by a chemical reaction in the treatment solution. Sludging can be caused by temperature, acidity changes, wood extractives, iron contamination and minerals in the water. It covers all the solid paste and other suspensions that accumulate in, among other places, pressure cylinder door sumps, open tanks (hot or cold open tank process) and flooding pits and at the bottom of working tanks. D.3.3 Spillages All spillages shall be reported to management, in accordance with the relevant national legislation (see foreword). (See also D.7.4.) Minor contained spills can be a) brushed or directed into the pit or sump and pumped into the appropriate storage tanks, or b) soaked up with an absorbent material such as sand, placed in suitable containers and disposed of as toxic waste by a registered waste management company.

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D.4 Post-treatment handling D.4.1 Freshly treated timber All freshly treated timber shall be drip free before dispatch. In the case of timber treated with CCA, the timber should be stacked for a period of time which will allow for sufficient fixation of the CCA chemical before it is dispatched to the purchaser or end user. Excess chemical solution shall be kept for re-use in the treatment process or for safe disposal (see D.2.2.10.2, D.3.2 and D.3.3). D.4.2 Manual removal from treatment vessel Special care shall be taken to avoid direct contact of the chemicals with the body when timber is being extracted by hand. Gloves and protective clothing shall be worn (see D.5.2). D.4.3 Cleaning the storage and bogie rail drip pads To prevent dust from waterborne preservatives accumulating on a concrete drip pad area, the drip pad areas shall be hosed down at least once a week and the washings shall be collected for re-use (see D.2.2.10.2.2). D.5 Health risks D.5.1 Training D.5.1.1 Plant operators and workers shall be instructed and trained in the correct handling and use of the treatment chemicals. Training shall be carried out by qualified competent person(s) and shall include emergency procedures in the case of a personal accident or an exposure to spillage. The quality control manager and the safety officer shall also be trained. D.5.1.2 All training shall be provided for by management on an ongoing basis as required by the relevant national legislation (see foreword). Records shall be kept of all training done by the employees. D.5.2 Personal protective equipment D.5.2.1 General Personnel shall remove their protective clothing when they leave the treatment area and shall put it on again before they re-enter. Provision shall be made for protective clothing for visitors to the treatment area. The basic protective clothing and accessories that shall be provided, and the applicable standards, are listed in table D.2. D.5.2.2 Head and eye protection Personnel who open drums, mix chemicals or open the treatment vessel door shall wear hard hats with face visor or goggles, in order to protect the head and face and especially the eyes.

Table D.2 — Basic protective clothing and accessories

1 2 Item Description

Hard hat Made of ABS plastics with polyethylene suspension, adjustable hat Face visor or goggles Made of clear polymethylmethacrylate, with plated metal harness to fit Respirator Covers nose and mouth with replaceable filter pad. Barrier cream Forms a very efficient barrier to the action of preservative chemicals on

the skin. Seek advice on the correct cream to use for each preservative. (This information is available from the preservative supplier.)

Gloves Fabric reinforced PVC. Excellent chemical resistance and physical protection

Safety suit or overall Special design in woven polypropylene gives the operator good


protection from dust or splashes of preservative and is itself unaffected by chemicals. The overall shall be washed after 2 d to 3 d usage.

Apron PVC or rubber type to be worn over the overal Footwear PVC gum boots

D.5.2.3 Nose and mouth protection A nose and mouth respirator shall be worn when powder or crystalline preservatives are being opened and mixed. The respirator filter pad shall be changed regularly or disposable face masks shall be worn. When the door of a treatment vessel is being opened, a respirator and face mask shall be worn to prevent inhalation of the fumes. Respirators and face masks shall be capable of controlling the exposure to below the occupational exposure limit (OEL) for the relevant hazardous chemical substance (HCS). D.5.2.4 Hand, arm and face protection A water-resistant and chemical-resistant barrier cream shall be available. When handling treated timber, mixing treatment chemicals, opening chemical drums or operating the treatment plant, personnel shall wear strong PVC-coated gloves. Contaminated gloves shall not be worn outside the treatment area. It is recommended that persons with skins sensitive to the treatment chemical used should not be allowed to work in the treatment area. D.5.2.5 Body protection When duties are being carried out within the treatment area, a PVC apron shall be worn over the overall in order to protect the body. The recommended overall has no pockets and is acid resistant; it should be laundered frequently on site. The laundry water may be added to other contaminated water (see D.1.2). D.5.2.6 Foot protection PVC gum boots fitted with safety toecaps provide the best foot protection. Alternatively, safety shoes could be recommended for warm climates, but not on sites that are likely to be muddy and wet. D.5.2.7 Maintenance of protective equipment All protective clothing and equipment shall be inspected on a regular basis to ensure that they are kept in good condition and efficient working order fit for the purpose intended. D.6 Plant emergency equipment The following minimum plant emergency equipment shall be available and easily accessible at all timber treatment plants: a) spade; b) stable broom; c) bucket (preferably PVC); d) suitable fire-fighting equipment; and e) bags of neutralizing chemicals (kept under lock and key), and instructions for use (as supplied by the chemical supplier or the manufacturer). D.7 Accident prevention, safety and first aid D.7.1 Safety awareness Selected posters, banners and slogans relating to safety in the workplace shall be displayed at strategic points at the treatment plant. Screening of safety films can effectively promote safety awareness. D.7.2 Labelling of chemicals Safety labels, as required by the relevant government department (see foreword), shall be available for all the relevant chemicals used.

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D.7.3 First-aid kit A complete first-aid kit shall be available at the treatment plant near the treatment area. All emergency medication, for example for burns, chemicals in eyes, chemical inhalation or ingestion, shall be available. The first-aid equipment shall never be situated in the same room as the chemicals. D.7.4 Material safety data sheets (MSDSs) MSDSs obtained from suppliers or manufacturers of the treatment chemicals shall be displayed in the operator's office or control room and in other strategic positions. Material safety data sheets shall include first-aid treatment and emergency spillage procedures for the preservative chemicals used in the treatment plant.


Table D.2 — Basic protective clothing and accessories

1 2

Item Item Description

Hard hat Made of ABS plastics with polyethylene suspension, adjustable hat size.

Face visor or goggles

Made of clear polymethylmethacrylate, with plated metal harness to fit the helmet.

Respirator Covers nose and mouth with replaceable filter pad.

Barrier

cream

Forms a very efficient barrier to the action of preservative chemicals on the skin. Seek advice on the correct cream to use for each preservative. (This information is available from the preservative supplier.)

Gloves Fabric reinforced PVC. Excellent chemical resistance and physical protection.

Safety suit or overall

Special design in woven polypropylene gives the operator good protection from dust or splashes of preservative and is itself unaffected by chemicals. The overall shall be washed after 2 d to 3 d usage.

Apron PVC or rubber type to be worn over the overall.

Footwear PVC gum boots.

DUS 2021:2019


Annex E (Normative)

Checklist for conformity assessment of treatment plant area The checklist in table E.1 shall be used to indicate requirements strictly to be followed in order to conform to the standard and from which no deviation is permitted.

Table E.1 — Checklist for treatment plant area compliance

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Item Criterion Remark

1 Occupational hygiene

1) Have emergency showers and eyewash facilities been installed within the bunded area?

2) Is contaminated water from the showers and eyewash facilities contained or recovered?

3) Is the policy of no eating, drinking or smoking applied by means of visible warning signs?

4) Is storm water diverted from the treatment plant?

5) Have provisions been made for contaminated storm water to be contained?

2 Safety 2.1 Chemical safety programme

Has a chemical safety programme been introduced that includes the following: a) A monitoring programme for workers’ health? b) Appointing a person responsible for occupational health and safety? c) Are only registered chemicals used and is the relevant information on handling storage and first aid up to date? d) Controls to ensure that correct handling and safety procedures are followed by employees? Information on and training in the above? e) Information on and training in the above? f) Ongoing liaison with local emergency services regarding chemical safety procedures?

2.2 Plant safety

a) Bunded area 1) Are all the constituent parts of the timber treatment plant within the bunded area?

2) Are the floor and wall impervious?

3) Can it contain the total contents of the plant plus 10 %?

4) If there is a separate bunded tank farm, can it accommodate a chemical volume as calculated in table D.1? Table D.1

5) If there is no roof over the treatment plant, can the pit or bunded area contain the total contents of the plant plus 10 % plus an allowance for a 1 in 50 year flood?


Table E.1 (continued)

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b) Treatment vessel 1) Is the door positioned so as to contain any spillage within the pit (or bunded area)?

2) If the vessel is coded, is it inspected in accordance with the requirements of the relevant national legislation (see foreword)?

3) Is the door seal clean and in a good workable condition?

4) Is storm water diverted from the treatment plant?

5) Is there a vessel-door warning sign indicating that the vessel is empty when vessel is not in operation?

6) If the door is not a bolted type, does it have a mechanical fail-safe system?

7) Has a pressure-relief valve been fitted?

8) Is a second pressure-relief valve required?

9) If a vacuum chest is linked into the vacuum line, is there a valve between the vessel and the vacuum chest?

10) Is the vacuum chest fitted with a sight glass or a level switch?

11) If the vessel is defined as a pressure vessel, does it have the required information marked on it?

12) Are the internal rails aligned and clear?

4) If the door has a single bolt hanger, does it have a safety chain?

5) If there is no roof over the treatment plant, can the pit or bunded area contain the total contents of the plant plus 10 % plus an allowance for a 1 in 50 year flood?

13) Is there an anti-float system?

c) Tanks 1) Are the tanks externally or internally painted? (Mild steel tanks only)

2) Are they mounted on a firm foundation within the bunded area or tank farm?

3) If mild steel tanks are used, are they elevated above the ground?

4) If they contain oil-based or light organic solvent preservatives, are they well vented?

5) If the tanks are closed, do they have inspection manholes?

6) If the tanks are open, do they have handrails?

7) Do the above-ground working tanks (excluding creosote tanks) have sampling taps?

DUS 2021:2019



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c) Tanks (concluded

8) Is each tank legibly and durably

marked with the following information:

a) Total tank capacity, in litres?

b) Construction material?

c) Wall thickness, in millimeters? )

d) The type of treatment solution

contained in the tank?

e) In the case of measuring and

mixing tanks, the tank capacity, in

litres per millimeter of depth?

9) Do the tanks have a closed-circuit

overflow system?

d) Pipe work and valves

1) Are the pipes protected against damage?

2) Are the pipes protected against corrosion?

3) Are the pipes easily accessible?

4) Are the valves easily accessible?

5) Do the valves leak?

6) Are the valves clearly labelled?

7) Do the overflow pipes form part of a

closed-circuit system?

e) Water supply If there is no ball float valve, does the water supply

pipe fill the tank from the top?

f) Mixer and mixing process

1) If present, has the mixer been designed to prevent

liquid from splashing and spilling from the mixing

tank?

2) Is the mixing solution introduced to the storage

tanks via a closed-circuit system?

3) If the chemical is a liquid or paste, is it introduced

into the mixing tank via a dosing vat?

4) Does the mixing tank have a perforated cage (for

powders only)?

5) Does the mixing tank have side baffle fins to

prevent rotation (if an agitator is used)?

6) Are drum washers used to empty containers of

paste products?

7) Are there any high-pressure water jets

that could cause mist, which could

cause a health hazard?

g) Pumps 1) Do the pumps (including couplings and

motor shafts) have protective guards?

2) Is gland leakage led into the sump or

pit for recovery?



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Item Criterion Result

h) Electrical control panel

1) Is there a locked-door signal (automated plants only)?

2) Is the electrical panel under cover?

3) Are the switches and isolators labelled?

4) Is the control panel in working order?

5) Are there flameproof motors (oil-based and light organic solvent preservatives only)?

i) Winches If the plant has winches, then

1) Does the winch have overload protection?

2) Is there a drum guard?

3) Does the winch have a foot-switch (bollard winches only)?

4) Is there a non-latching dead man’s switch (drum winch only)?

j) Treatment and D.2.2.10.1 storage area demarcation

1) Is the treatment plant area demarcated?

2) Is the treated timber storage area demarcated?

k) Drip pads If the process has no final vacuum

1) Is there a storage drip pad?

2) Can it accommodate timber treated over a 24 h period plus 10 %?

3) Is it positioned adjacent to the treatment plant?

4) Is it constructed from impervious materials?

5) Does it drain into the pit or bunded area so that excess chemical solution can be kept for re-use?

6) Is there a bogie rail drip pad provided at the bogie rails and

a) Is it at least as long as the vessel?

b) Is it constructed from impervious materials?

c) Is it positioned adjacent to the treatment plant?

d) Does it drain into the pit or bunded area?

l) Housekeeping 1) Is waterborne deposit build-up in the treatment plant area regularly hosed down and collected for re-use or suitable disposal?

2) In the case of oil-borne preservatives and LOSPs, is the build-up regularly soaked up with sawdust and disposed of?

DUS 2021:2019



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Item Criterion Result

2.3 Operator's office or control room

1) Is an operator’s office or control room provided?

2) Does it have adequate lighting?

3) Is it well ventilated?

4) Is it accessible to authorized personnel only?

5) If the control room is used as a laboratory, are all the samples removed and returned to the treatment plant after analysis?

6) Are MSDSs of the chemicals displayed in the control room?

2.4 Chemical off- loading and storage area

1) Are the chemical off-loading and storage areas clearly demarcated?

2) Is the chemical off-loading and storage area constructed from impervious materials?

3) Can spillages be contained in the loading and storage area?

4) If not, do they drain into the pit or bunded area?

5) Is the chemical kept in a lock-up storage area or tank?

6) Is a stock book kept of all chemicals received?

3 Waste management and disposal 3.1 Storage

1) Are empty containers stored in the lock-up storage area?

2) Is the chemical sludge stored in appropriate containers?

3) Are these containers of chemical sludge stored in the pit or bunded area?

3.2 Disposal 1) Is treated timber waste disposed of in an approved manner ?

2) Are all used containers neutralized and returned to the chemical supplier, or disposed of in an approved manner?

3) Is all contaminated sawdust, sand, etc., disposed of in an approved manner?

4) Is the chemical sludge disposed of in an approved manner?

3.3 Spillages 1) Are spillages reported?

2) Has provision been made for minor spillages to be contained within the bunded area?

3) Is absorbent material available to soak up minor spillages?



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4 Post-treatment Handling

4.1 Freshly treated timber

1) Is all the freshly treated timber drip free before dispatch?

2) Has the timber treated with CCA been stacked for a period of time to allow for sufficient fixation of the CCA chemical before being dispatched to the purchaser or end user?

4.2 Manual removal D.4.2 from treatment vessel

1) Has special care been taken to avoid direct contact of the chemical with the body when extracting timber by hand?

2) Are records kept for the training done by each employee?

4.3 Cleaning the storage and bogie rail drip pads

1) Are the drip pad areas hosed down at least once a week?

Health risks 5.1 Training

1) Have the plant operators and workers been trained in the correct handling and use of treatment chemicals as well as the emergency procedures in the case of an incident?

2) Are records kept for the training done by each employee?

5.2 Personal protective equipment (PPE)

1) Has the appropriate PPE been issued to people working with preservative chemicals and freshly treated timber and is it used?

2) Is the appropriate PPE available for visitors?

3) Is the PPE removed before leaving the treatment plant area and put back on before re-entering?

4) Is the PPE maintained and kept in good working condition, and is it fit for its intended purpose?

6 Plant emergency equipment

1) Is the emergency equipment listed in D.6 available and in close proximity to the treatment plant?

2) Are the neutralizing chemicals kept under lock and key?

7 Accident prevention, safety and first aid

1) Is safety awareness being promoted by means of posters, banners or slogans?

2) Are safety labels available for the chemicals used?

3) Is a complete first-aid kit available at the treatment plant (not in the same room as the chemicals)?

4) Apart from the control room, are MSDSs displayed in strategic positions in the treatment plant area?

DUS 2021:2019


Bibliography

[1] ISO #####-#, General title — Part #: Title of part

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Certification marking

Products that conform to Uganda standards may be marked with Uganda National Bureau of Standards (UNBS) Certification Mark shown in the figure below.

The use of the UNBS Certification Mark is governed by the Standards Act, and the Regulations made thereunder. This mark can be used only by those licensed under the certification mark scheme operated by the Uganda National Bureau of Standards and in conjunction with the relevant Uganda Standard. The presence of this mark on a product or in relation to a product is an assurance that the goods comply with the requirements of that standard under a system of supervision, control and testing in accordance with the certification mark scheme of the Uganda National Bureau of Standards. UNBS marked products are continually checked by UNBS for conformity to that standard.

Further particulars of the terms and conditions of licensing may be obtained from the Director, Uganda National Bureau of Standards.

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