m1version3oct2005_1

Technical Guidance Note(Monitoring) M1

Sampling requirements for stack-emission monitoringEnvironment Agency

October 2005

Version 3

Record of amendments

Versionnumber

Date Amendment

2 July 2002 Added details on the use of temporary platforms to section 4.1.1.3 Oct 2005 Added details on conducting a swirl test (Section 2.1.3).3 Oct 2005 Added details on criteria for selection of gas sampling location (Section

2.2.3).3 Oct 2005 All references to BS 3405:1983 and BS 6069:Section 4.3:1992 deleted.3 Oct 2005 Amendments to positional requirements for CEMs (Section 3.2).3 Oct 2005 Section 4.1.1 amended to reflect requirements of HSE Work at Height

Regulations 2005.3 Oct 2005 Revised access port requirements (Figure 4.5).

Foreword

PurposeThis Technical Guidance Note (TGN) on sampling requirements for monitoring stack-emissions to air from industrial applications is one of a series providing guidance toEnvironment Agency staff, monitoring contractors, industry and other partiesinterested in stack-emission monitoring. It is also a key reference document insupport of our Monitoring Certification Scheme (MCERTS) and Operator MonitoringAssessment (OMA).

It provides guidance on:

the selection of the sampling position, sampling plane and sampling points; access, facilities and services required; safety considerations.

Throughout the document, references to sampling from stacks should be interpreted asalso meaning sampling from vents, ducts and flues, unless otherwise stated.

The section on safety draws attention to the importance of health and safety in stack-emission monitoring, provides guidance on the hazards and risks associated withstack-emission monitoring and highlights the relevant health and safety legislation.

How to use M1The TGN is divided into four chapters. Chapter 1 describes the main monitoringapproaches, the fundamental principles of sampling and the importance of amonitoring strategy. Chapters 2 and 3 give guidance on the sampling requirementsfor periodic stack-emissions measurements and continuous emissions monitoringsystems, respectively. Chapter 4 provides guidance on sampling facilities and safetyrequirements for stack-emission monitoring.

Contents

1. Monitoring approaches1.1 Monitoring strategy 11.2 The different approaches to monitoring stack-emissions 21.3 The importance of representative sampling 2

1.3.1 Fundamental principle 21.3.2 Representative sampling of particulates and gases 2

1.4 Choice of sampling method, sampling technique and equipment 4

2. Sampling requirements: periodic measurements2.1 Periodic sampling of particulates 4

2.1.1 Special characteristics 42.1.2 Positional requirements for sampling particulates 52.1.3 Criteria for locating the sampling plane 62.1.4 Surveying the proposed sampling plane 82.1.5 Preliminary velocity survey 82.1.6 Unacceptable characteristics 82.1.7 Number of sampling points 92.1.8 Position of sampling points along the sample lines 9

2.1.8.1 Position of sampling points for circular stacks 102.1.8.2 Position of sampling points for rectangular and square stacks 11

2.2 Periodic sampling of gases 132.2.1 Special characteristics of sampling gases 132.2.2 Location requirements for monitoring gases 142.2.3 Criteria for locating a sampling plane for gas concentrations 15

2.2.3.1 Procedure for conducting a stratification test 162.2.4 Number and position of sampling points for sampling gases 16

3. Sampling requirements: continuous emissions monitoring systems3.1 CEMs measuring concentrations 173.2 CEMs measuring gas volumetric flow rates 17

4. Sampling facilities and safety requirements for stack-emission monitoring4.1 Access and facilities for periodic monitoring 18

4.1.1 Safe working platform and means of access to the sampling position 184.1.2 Space for the equipment and personnel 194.1.3 Means of entry into the stack (sampling access ports) 194.1.4 Essential services 264.1.5 Other issues 26

4.2 Access and facilities for periodic monitoring of gases 264.3 Access and facilities for CEMs 264.4 The risk-management approach to site work 27

4.4.1 Safety has the highest priority 274.4.2 Prominent hazards encountered when stack-emission monitoring 284.4.3 The risk assessment process 284.4.4 Responsibilities 294.4.5 When to carry out a risk assessment 304.4.6 Getting the operator involved 304.4.7 Reporting of accidents and near misses 314.4.8 Further guidance 31

5. Status of this document 32

Annex 1 Sample point requirements as specified in ISO 9096:2003 33

References 34

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Sampling requirements for stack-emission monitoring

1. Monitoring guidance

The Environment Agency publishes Technical Guidance Notes (TGNs) to provideadvice and support in relevant subject areas. This TGN covers sampling and safetyrequirements for stack-emission monitoring. It is one of a series of TGNs in the Mseries providing guidance on regulatory monitoring.

The Environment Agencys MCERTS scheme (see Box 1.1) includes both continuousemission monitoring systems (CEMs) and manual stack-emission monitoring.MCERTS for manual stack-emission monitoring provides for the assessment of themanagement, quality and reliability of organisations, and the competence ofindividuals carrying out stack-emission monitoring against published performancestandards for organisations1 and personnel2. This TGN is a key reference documentthat underpins MCERTS for manual stack-emission monitoring and providesguidance on suitable sampling locations for CEMs.

1.1 Monitoring strategy

Emission monitoring carried out at a stack must be fit-for-purpose. To meet thiscriterion, considerable thought must go into developing an appropriate monitoringstrategy for the particular application.

This monitoring strategy should be documented in a site-specific protocol (SSP),which is generated by the monitoring organisation before monitoring work begins.The SSP describes how the method will be employed in a given, specific situation andshould be undertaken for each site where monitoring is to take place. The MCERTSperformance standard for organisations1 sets out the requirements for the SSP.

Box 1.1 MCERTSMCERTS is the Environment Agency's Monitoring Certification Scheme for instruments,monitoring and analytical services. The scheme is built on proven international standardsand provides industry with a framework for choosing monitoring systems and services thatmeet the Environment Agencys performance specifications. MCERTS reflects thegrowing requirements for regulatory monitoring to meet European and internationalstandards. It brings together relevant standards into a scheme that can be easily accessed bymanufacturers, operators, regulators and laboratories. Further information on MCERTS isavailable at www.mcerts.net

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1.2 The different approaches to monitoring stack-emissions

Stack-emissions monitoring can be classified into two types:a) Periodic measurements a measurement campaign is carried out at

periodic intervals, for example, once every three months. The sampleis usually, but not always, withdrawn from the stack (extractivesampling). An instrumental or automated technique may be used,where the sampling and analysis of the substance is fed to an on-lineanalyser. Alternatively, a technique may be used where a sample isextracted on site and analysed later in a laboratory. Samples may beobtained over several hours, or may be so-called spot or grabsamples collected over a period of seconds to several minutes.

b) Continuous emissions monitoring systems (CEMs) automatedmeasurements carried out continuously, with few if any gaps in thedata produced. Measurement may be carried out in situ in the stack (forexample, cross-duct monitoring), or extractive sampling may be usedwith an instrument permanently located at or near the stack. CEMs arealso referred to as Automated Monitoring Systems (AMS), particularlyin a European context.

This TGN uses the convenient division into periodic measurements and CEMs whendescribing the requirements for sampling positions, access, facilities and services insubsequent chapters.

1.3 The importance of representative sampling

1.3.1 Fundamental principle

The fundamental principle behind any sampling activity is that a small amount ofcollected material should be representative of all the material being monitored. Thenumber and location of samples that are needed to make up a representative sampledepends on how homogeneous the material is. If it is very homogeneous, only a fewsamples may be required. If the material is heterogeneous, many more samples willbe required.

1.3.2 Representative sampling of particulates and gases

This fundamental principle applies as much to sampling stack gases as it does to anyother type of sampling. Although the gas in a stack might be thought of as beingmore uniform than, for example, a stockpile of coal, gases in stacks can become non-homogeneous. This may be due to differences in chemical composition, ordifferences in temperature and velocity, which may lead to stratification and swirling.Where the gas is also carrying particulates along the duct, there is likely to be evenless homogeneity. Here, special measures must be taken to ensure samples arerepresentative.

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For gases carrying particulates, the sampling approach has to address two effects.Firstly, inertial effects introduced by gravity and the duct geometry lead to theparticles being unevenly distributed in the duct. Samples must be obtained frommultiple sample points (see to Box 1.2 for definitions of terms) across the samplingplane to give an overall average of the particulate emission. Rules have beendeveloped specifying exactly where these sampling points should be located (theseare described in Section 2.1.8). In the case of a cross-duct CEM monitoringparticulates, the average particulate concentration is obtained as an integratedmeasurement across the duct. Secondly, for extractive methods, the sample must becollected isokinetically (see Box 1.3).

Box 1.2 Definition of important terms in stack emission monitoring

Isokinetic sampling is achieved when the gas enters the sampling nozzle at exactly thesame velocity and direction as the gas travelling in the stack..Sampling location a suitable position on stack, duct or flue where representativesamples can be obtained.Sampling plane or sampling section the plane normal to the centreline of the stack, ductor flue at the sampling position.Sampling point the specific position on the sample plane from where the sample isextracted.Sampling ports or access ports points in the wall of the stack, duct or flue throughwhich access to the emission gas can be gained.Stack, duct, flue, vent a structure through which pollutants are released to atmosphere.Typically stacks are intended to be of sufficient height to adequately disperse emissionsin the atmosphere. Ducts and flues are usually a lower height and often located beforeentering a stack. Vents are not usually free-standing structures.Sampling lines imaginary lines in the sampling plane along which sampling points arelocated, bounded by the inner wall of the stack, duct or flue.

Box 1.3 The importance of isokinetic sampling for particulates

Due to the wide range of particle sizes normally present in process emission streams, it isnecessary to sample isokinetically to ensure that a representative sample of the particulateemission is obtained.

If the sampling velocity is less than the isokinetic rate, at first sight it would appear, thatthe emission will be underestimated. However, because the sampling rate is too low,there is a divergence in flow around the sampling inlet. Small particles are able to followthe flow and a percentage of them will not be sampled. Larger particles, on the otherhand, are not able to follow the flow because of their greater inertia and more of theseparticles will enter the sampler. Thus a sub-isokinetic sampling rate will lead to a bias inthe sampled particle size distribution towards the larger particles. This could lead to anoverestimate of the particulate concentration depending on the original size distribution.

Sampling at a rate in excess of the isokinetic rate will lead to a bias in the sampledparticle size distribution towards the smaller particles. This could lead to anunderestimate of the emission concentration depending on the original size distribution.

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Where the measurement concerned is of concentrations of gaseous species alone, theapproach is to choose a sampling location where the gases are well mixed. Samplingcan often be from a single sampling point in the sampling plane. However, if the massemission rate is to be calculated, the gas volumetric flowrate will need to bemeasured; this will require temperature and velocity measurements to be made atseveral points across the sampling plane.

Some pollutants; for example, metals and dioxins, are present in both particulate andvapour phases. Other pollutants for example, hydrogen chloride, may be present in anaerosol phase and vapour phase. Aerosols are normally treated as particulates. In allsuch cases isokinetic multi-point sampling is required, as described in Section 2.1.

1.4 Choice of sampling method, sampling technique and equipment

There is a wide choice of monitoring approaches, analytical techniques, publishedmethods and equipment that can be used to carry out stack-emissions measurements.It is important that each of these is chosen to be suitable for the application inquestion. TGN M2 Monitoring of Stack Emissions to Air3 gives detailed guidance ondeciding which approach, technique and method should be chosen.

The sampling approach, technique, method and equipment that are chosen can havedifferent effects on the requirements for access, facilities and services. Though theprecise requirements can vary, the following will always be required:

a safe means of access to the sampling position; a means of entry for sampling equipment into the stack; adequate space for the equipment and personnel; provision of essential services, such as electricity.

Further details on such requirements are given in Chapter 4.

2. Sampling requirements: periodic measurements

2.1 Periodic sampling of particulates

2.1.1 Special characteristics

Periodic sampling of particulates requires extractive isokinetic sampling methods.The principle of isokinetic sampling is that a sharp-edged nozzle is positioned in thestack facing into the moving gas stream and a sample of the gas is extracted throughit, at the same velocity as the gas in the stack, for a measured period of time. Toallow for non-uniformity of particulate distribution, samples are taken at a pre-selected number of stated points across the sample plane. The particulates collectedin the sampler are later weighed, and the concentration of particulate matter in thestack is calculated using the volume of gas sampled. The mass flow rate of particulatematter in the stack can be calculated from the concentration and the velocity of gas inthe stack.

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Some of the older measurement standards are prescriptive (either explicitly orimplicitly) about the equipment that can be used for sampling particulates. The trendnow, however, is towards standards that lay down minimum performance and designcriteria for the equipment. Any piece of sampling equipment can be used if it meetsthese criteria and is fit for purpose. This last caveat is important as each system mayhave particular advantages and drawbacks. These need to be considered whenchoosing the most suitable sampling equipment for the measurement in question.

The main differences between particulate sampling equipment, in so far as they affectthe access, facilities and services required, is the configuration of the sample probeand particle-separator device. Sampled particulate is collected on a filter held in afilter holder; the latter may be arranged on the probe so that it is in the stack (in-stackfiltration) or out of the stack (out-of-stack filtration).

2.1.2 Positional requirements for sampling particulates

There are a number of standard methods for monitoring particulates. The ComitEuropen de Normalisation (CEN) standard BS EN 13284-1:20024 details thepositional requirements for particulates and is referred to on positional requirementsby a number of other CEN standards. It should be noted that BS EN 13284-1:20024along with another particulate standard BS ISO 90965 covers the measurement ofparticulates in the range from 0 to 1000 mg m-3.

This chapter provides a single set of requirements for sampling positions forisokinetic sampling of particulates and multi-phase pollutants. These requirements aretaken from BS EN 13284-1:2002.

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2.1.3 Criteria for locating the sampling plane

The general approach for periodic sampling of particulates and aerosols can besummarised as:

Sampling must be carried out at a suitable location on the stack. Bends, branches,obstructions, fans and leaks can all cause undesirable variations in the temperatureand velocity profiles, which may make the location unsuitable for sampling.For new installations, the sampling plane should be located according to therequirements contained in Table 2.1. By adhering to these requirements, there is avery good chance that the flow-stability criteria defined in Table 2.2 will be met. Theflow-stability criteria of a gas encompass velocity and direction. Flow criteria is usedin this TGN as a term to cover all these parameters. It should be emphasised that it isthe flow criteria that are important, not the adherence to the positional requirementsper se. Therefore on plants where the sampling plane location does not meet therecommendations in Table 2.1, it is possible to locate the sampling plane at anotherlocation as long as the flow criteria are met.

Identify a potentially suitable samplinglocation (covered in this section)

Access the stack and check that the gas-flowcriteria are met by carrying out an exploratorysurvey (see Sections 2.1.4 and 2.1.5)

Decide the number and position of thesampling points (see Sections 2.1.7 and 2.1.8),and install ports and access to the samplinglocation (see Section 4.1).

Carry out preliminary velocity traverse(Section 2.1.5) to confirm satisfactory andproceed with sampling.

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Table 2.1 Recommended location for meeting sample location requirements forperiodic sampling of particulates

General location ofsampling plane

The sampling plane must be situated in a length of straight duct (preferablyvertical) with constant shape and constant cross-sectional area. Where possible,the sampling plane should be as far downstream and upstream from anydisturbance, which could produce a change in direction of flow (e.g. bend, fan ora partially closed damper).

Location of samplingplane in straightsection

The sample plane criteria are usually met in sections of duct with five hydraulicdiameters (see Box 2.1 for definition) of straight duct upstream of the samplingplane and two hydraulic diameters downstream. If the sampling plane is to belocated near the top of the stack outlet then the distance from the top should befive hydraulic diameters (making a straight length of 10 hydraulic diameters).

Table 2.2 Flow-stability criteria for periodic sampling of particulates

Angle of gas flow 15 from stack longitudinal axis

Flow direction No local negative flow

Minimum velocity Dependant on the method used (for Pitot tubes a differentialpressure larger than 5 Pa)

Gas velocities variations Ratio of highest to lowest local gas velocities less than 3:1

Note: The reader is advised to consult the normative requirements contained withinAnnex B of BS EN 13284-1 :20024 for guidance on how to carry out a swirl test witheither an L Type or and S Type Pitot tube.

Compliance with the flow criteria should be checked by a preliminary velocity survey(Section 2.1.5). If the flow criteria in Table 2.2 are not met, the sampling location isnot in compliance and a more suitable sampling location should be selected.However, problems with meeting the criteria sometimes occur with older installationswhere it is not always practicable to move the sampling plane to a better locationbecause of safety considerations, cost, or the design of the stack. When this occurs itmay be possible to improve representative sampling by increasing the number ofsampling points above those specified in Tables 2.3 and 2.4.

Box 2.1 Definition of hydraulic diameterIt is not possible simply to use the term diameter in positional criteria, because not all stacks are ofcircular cross-section. To allow all shape ducts to be included, the term hydraulic diameter is used,defined as:

(4 x area of sampling plane) / length of sample plane perimeter

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2.1.4 Surveying the proposed sampling plane

An exploratory survey of the proposed sample plane should be undertaken. Thisshould include a stack-gas velocity survey, as described in Section 2.1.5. For metal orother thin-walled ducts or chimneys, 13mm (half inch) diameter pilot holes, drilledthrough the flue wall on the centres of the proposed sample access holes, may enablea small bore Pitot-static tube and thermocouple probe of suitable length to be used forthis purpose. The use of such temporary access holes distinguishes the exploratoryvelocity traverse from the preliminary velocity survey. The latter must be performedthrough permanent access ports meeting the requirements in Section 2.1.5.

It is important that this approach is followed, so that the sample plane location isshown to be suitable before installing comprehensive and expensive sampling accessand facilities on a stack.

2.1.5 Preliminary velocity survey

A preliminary velocity traverse should be carried out before sampling is carried out ata location for the first time. To establish that a sampling location is suitable,measurements of gas velocity should be carried out at a minimum of ten equallyspaced points along each proposed sampling line. Sampling points should be locatedeither more than 3% of the sampling line length or more than 5cm whichever is thegreater value from the duct wall. Measurements at these sampling points mustdemonstrate that the gas stream at the sampling plane meets the requirementscontained in Table 2.2. If the results do not conform to the flow-stability criteria,another sample location should be found.

2.1.6 Unacceptable characteristics

Some older installations may not meet the flow-stability criteria, but sampling maynevertheless still be required. Deviations from the standard can have significanteffects on measurement uncertainty.

Information on assessing the effects of deviations on accuracy is given in the SourceTesting Association (STA) Quality Guidance Note QGN001 r16

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2.1.7 Number of sampling points

The number of sampling points which is to be used is determined by the size of thestack. The minimum number of sampling points and sample lines are shown in Tables2.3 and 2.4, for circular and rectangular stacks respectively. The sample pointrequirements contained in ISO 9096:20035 are detailed in Annex 1.

Table 2.3 Minimum number of sampling points for circular stacks

Range of samplingplane areas

m2

Range of ductdiameters

m

Minimum number ofsampling lines

(diameters)

Minimum number ofsampling points per

plane

1.6 2 At least 12 and 4 per m2 b

a using only one sample point may give rise to errors that give an uncertainty above 10%.

b for large ducts, 20 sampling points is generally sufficient

Table 2.4 Minimum number of sampling points for rectangular stacks

Range of sampling plane areasm2

Minimum number of sidedivisions a

Minimum number of samplingpoints per plane

2.0 3 At least 12 and 4 per m2 c

Note a: Other side divisions may be necessary, for example if the longest stack side length is more than twice thelength of the shortest side (see Figure 2.4). Sample lines for square and rectangular stacks are explained in Section2.1.8.2.

Note b: Using only one sampling point may give rise to errors that give an uncertainty above 10%

Note c: For large ducts, 20 sampling points is generally sufficient.

2.1.8 Position of sampling points along the sample lines

The sampling plane is divided into equal areas and sampling is carried out from pointsin the centres of these areas. This is shown in Figure 2.1 for circular stacks and inFigures 2.2, 2.3 and 2.4 for square and rectangular ducts.

Sampling points should be located either more than 3% of the sampling line length ormore than 5cm whichever is the greater value from the duct wall.

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2.1.8.1 Position of sampling points for circular stacks

The sampling plane is divided into equal areas, the central one being circular (seeFigure 2.1). The sampling points are located along two or more sampling lines(diameters) at the centres of these equal areas.

Figure 2.1 Sampling in circular stacks (positions shown are for stacks >2 m indiameter)

12

3

4

d

Xi

The precise positions of the sampling points will depend on:

the number of sampling lines chosen; the number of sampling points that need to be used (see Table 2.3).A commonly encountered situation is a circular stack with two sample lines. In thiscase, a simple expression can be used to calculate the distance of each sampling pointfrom the duct wall.xi = Kid

where: xi is the distance (m) from the stack wall to an individual sampling point;Ki is a calibration factor (a percentage of the diameter);d is the duct diameter (m) at the sampling plane;i is the sample point identification position on the sample line.

Values for the factor K are given in Table 2.5 for different numbers of samplingpoints (nd) required along each of two sampling lines.

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Table 2.5 Position of sampling points as a percentage distance across a circularstack

Values of K (as a % of diameter) for different numbers of points (nd)(central point included)

Sample pointposition (i) on thesampling line nd = 3 nd = 5 nd = 7 nd = 9

1 11.3 5.9 4.0 3.02 50.0 21.1 13.3 9.83 88.7 50.0 26.0 17.84 - 78.9 50.0 29.05 - 94.1 74.0 50.06 - - 86.7 71.07 - - 96.0 82.28 - - - 90.29 - - - 97.0

Table 2.5 does not apply to circular stacks where more than nine sampling points areneeded or more than two sample lines are used. In such cases, the following generalformula should be used to calculate the distance of each sampling point in from theduct wall.xi = 0.5d [1-{((2nr-2.i+1)nd+1)/(2nr.ndia+1)}]where: i is sample point identification number* along the sampling line;

d is the inside diameter of the stack, i.e. the length of the sampling line (m);nr is the number of sampling points on a sampling radius (i.e. 0.5d); andndia is the number of sampling diameters (sampling lines).

There is also an alternative method, known as the tangential method, for determiningthe position of sampling points in circular stacks. This rule allows the approachcommon in the United States (that is, no sampling point at the centre of the stack).Details of the tangential method can be found in BS EN 13284-1:2002.

2.1.8.2 Position of sampling points for rectangular and square stacks

The sampling plane should be divided up into the required number of equal areas bylines parallel to the stack walls (see Table 2.4). The distance between each of theseparallel lines is known as a side division. Sampling points are located at the centresof the equal areas, also known as partial areas. Figure 2.2 shows the relationshipbetween the sample points in the centres of equal areas, the side divisions and thesample lines. Refer to Section 2.1 for details on where to install access ports to reachthese sampling points.

* The first point in from the access port is identified as position 1.

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Figure 2.2 Equal areas, side divisions, sampling lines for square/rectangularstacks

The most common case, shown in Figure 2.3, is for square and near-square stacks(where the ratio of the longer sides l1 to the shorter sides l2 of the stack is no morethan 2:1). The longer and shorter sides of the stack are both divided into an equalnumber of parts to meet the requirements of Table 2.4 for minimum numbers ofsample lines and sampling points. The number of partial areas, each having asampling point at its centre, is thus the square of the number of side divisions. Theseareas have the same shape as the stack.

Figure 2.3 Sampling positions in square/near-square stacks where sides l1 to l2 is2:1

l2

l1

Cross-sectionof stack

l2n2

l22n2

l12n1

l1n1

3 side divisions alongshortest side

3 sidedivisions

alonglongest

side


9 equal areas

9 samplingpoints

3 samplinglines

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For stacks with a more extreme rectangular aspect ratio (ratio of longer sides l1 to theshorter sides l2 is more than 2:1) a different approach is used, to avoid having long,thin partial areas. The procedure is to give stack side l1 more side divisions than l2, sothat the partial areas have a length to breadth ratio of no more than 2:1. This isillustrated in Figure 2.4.

Figure 2.4 Sampling positions in rectangular stack where sides l1 to l2 is >2:1

The requirements of Table 2.4 for minimum numbers of sample lines and samplingpoints must be met. The number of sampling points is calculated as follows: if thestack sampling plane sides l1 and l2 are divided into n1 and n2 parts respectively, then atotal of n1.n2 sampling points is obtained.

The distance between the stack wall and the first sample point will be l1/2n1 ifsampling was carried out from ports on side l2, or l2/2n2 if sampling was carried outfrom ports on side l1.

2.2 Periodic sampling of gases

2.2.1 Special characteristics of sampling gases

For monitoring gases, the range of sampling equipment and apparatus is very wide.However, they can be grouped conveniently into automated techniques and manualtechniques (see Box 2.2). The main steps in measuring gaseous pollutants are asfollows:

l2

l1


l22n2

l2n2

l12n1

l1n1

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When gases are measured using automated/instrumental techniques, such as gasanalysers, Stage 2 is omitted, and the sample goes directly to the analysis stage (Stage3). In contrast, when gases are measured using manual techniques, Stage 3 is usuallycarried out away from the site at an analytical laboratory.

The particular sampling-train configuration will vary according to the substance andthe process conditions, for example whether the gas stream is hot or cool, wet or dry,and whether sampling is to be performed in an intrinsically safe area. For instance, acool gas stream will require Stage 1 of the sample train to have a heated sample line;very wet gas streams may require drop-out pots. The sample train configuration mayaffect the requirements for access and facilities. For example, Stages 1 and 2 maytake place immediately after the sample probe, with the apparatus located on the stackaccess platform. Alternatively, an inert (and usually heated) sample line may be usedto bring the sample gas from the probe to Stages 2 and 3 at the base of the stack or ina mobile laboratory. It is also useful to consider the phase of the target species. Forexample, dioxins may adsorb onto the surface of particulate species, if present.Alternatively, if water droplets are present which may absorb hydrogen chloride,isokinetic sampling may be required.

2.2.2 Location requirements for monitoring gases

In principle, the location requirements for measuring gas concentrations are lessexacting than for particulates. The criteria for measuring gas concentrations alone aredescribed in Section 2.2.3.

Stage 1Representative sampleof source gas extractedthrough probe, filteredand conditioned

Stage 3The sampled substanceis analysed by anappropriate analyticaltechnique

Stage 2Gaseous substancesadsorbed on, orabsorbed in, anappropriate collectionmedium

Box 2.2 Automated and manual techniquesFor automated techniques, the sampling and quantification stages are conventionally consideredto take place almost simultaneously, within an analyser. With manual techniques, the sample istaken, then the quantification and analysis takes place as a discrete, later stage.

Automated/ instrumental techniques

Manual techniques

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However, in regulatory compliance monitoring it is common for mass emissions rates(for example, g s-1) to be reported. Calculation of mass emissions rate requires themeasurement of gas volumetric flow-rate through the duct. This requires temperatureand velocity measurements to be taken at different points across the sampling plane.Measurements to determine stack-gas velocity and volumetric flowrate should bemade in accordance with ISO 10780:19947. A suitable sampling location shouldtherefore conform to the flow-stability requirements described in Table 2.2.

Even in cases where no estimate of mass emissions rate is required, the processoperator should think carefully about upgrading the sampling plane in case massemissions are required in the future. For this reason, it is recommended that whereverpossible the sampling position is chosen to comply with the same criteria as whensampling for particulates.

2.2.3 Criteria for locating a sampling plane for gas concentrations

Sampling should be carried out from a sampling position where the gases arehomogeneous and there is positive gas flow. This can be checked by a surveyfollowing the basic principles in Section 2.1.4, but using a direct-reading instrumentto traverse the proposed sampling lines. The stack gas at the proposed samplingposition is classed as homogeneous if differences in concentration across the duct donot exceed 10% as specified in ISO/DIS 103968 (see below). The proximity to bends,branches, obstructions and fans is less important when measuring gas concentrationsonly, as variations in the temperature and velocity profiles tend not to influence theresult. However, sampling in the vicinity of air in-leakage must be avoided. Singlepoint sampling for gaseous species should only be undertaken after an acceptabledegree of homogeneity has been demonstrated. Special care should be exercised ifgaseous sampling is being undertaken using access ports located in the vicinity ofthose selected for particulate measurement. This because the in-duct conditions whichare desirable when sampling particulates, may also contribute to non-uniformdistribution of gaseous species.

Note: ISO 10396:19937 Stationary Source Emissions Sampling for the AutomatedDetermination of Gas Concentrations is currently being revised. The draft revisedstandard ISO/DIS 10396 contains more-detailed requirements for sampling planeselection for gas concentrations than the 1993 version. The account given below isdrawn largely from the revised, draft standard, ISO/DIS 10396.

Before any sampling is undertaken, it is necessary to determine any spatial ortemporal fluctuations in the gas concentrations, and to carry out a preliminary surveyof the gas concentration, temperature and velocity. Measure the concentration,temperature and velocity at the sampling points several times to obtain their spatialand temporal profiles. Conduct this survey when the plant is operating underconditions that will be adhered to during the test, in order to determine whether theselected sampling position is suitable and whether the conditions in the duct aresatisfactory. This survey could be omitted if the spatial or temporal fluctuations in theduct can be determined from the owners investigation, a previous investigation or theprocess characteristics in advance of the survey. In this case the information relatingto previous procedures for the determination of the sampling point and the adoption ofsingle point sampling shall be described in the report. It is necessary to ensure that the

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gas concentrations measured are representative of the average conditions inside theduct or stack. The requirements for the extractive sampling of gas may not be asstringent as those for particulate material. It is important that the sampling point is notlocated near any obstructions that could seriously disturb the gas flow in the duct orstack. The pollutant may have cross-sectional variation. The concentration at variouspoints of the cross-section shall first be checked, in order to determine if the presenceof gas stratification or air infiltration indicates that the gas to be measured is nothomogenous. If an alternative, acceptable, location is not available, multipointsampling is then required.

2.2.3.1 Procedure for conducting a stratification test:

With the process operating under steady-state conditions and at normal load, use atraversing gas sampling probe to measure the pollutant and diluent (CO2 or O2)concentrations at a minimum of twelve points located at sampling locations asspecified in ISO 9096. Use automated analytical methods for the measurement of thegas concentrations. Measure for a minimum of two minutes at each traverse point.While traversing, measure the pollutant and diluent gas concentrations from the centreof the stack to determine if temporal, rather than spatial variations in the flue gasconcentrations are occurring. Calculate the average pollutant and diluentconcentration at each of the individual traverse points. Then, calculate the arithmeticaverage concentrations for the gas from all of the traverse points. The pollutant ordiluent gas is said to be non-stratified (ie homogenous) if the concentration at eachindividual traverse point differs by no more than 10% from the arithmetic averageconcentration for all of the traverse points. Usually, the cross-sectional concentrationof gaseous pollutants is uniform, due to the effects diffusion and turbulent mixing. Inthis case, it is only necessary to sample at one point within the stack or duct todetermine the average concentration. A gas sample should be extracted near the centreof the sampling site, positioned one-third to halfway in the stack or duct. When usingnon-extractive systems, a representative location should be similarly selected.

2.2.4 Number and position of sampling points for sampling gases

Providing the gases are homogeneous, sampling of the gaseous pollutant can be froma single sampling point on the sampling line. For sampling pollutants in the gaseousphase, ISO 10396:1993 recommends positioning the tip of the sampling probebetween one-third and half-way into the stack to give a representative sample,provided:

an initial concentration traverse shows no significant differences in concentration(as defined in Section 2.2.3); and

for cases where mass emissions are to be calculated, the preliminary temperatureand velocity traverse results meet the flow criteria in Table 2.2.

Some pollutants, such as heavy metals, dioxins and PAHs, are present in both theparticulate phase and the vapour phase, while hydrogen chloride can exist in both asan aerosol and vapour phase. In most cases, the authorisation or permit will requirethe total emission to be reported, in which case both phases should be sampledsimultaneously and isokinetically at the sampling points described in Section 2.1.7.

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3 Sampling requirements: continuous emissions monitoring systems

3.1 CEMs measuring concentration

For CEMs measuring particulates, the location of the CEM is determined by therequirements of BS EN13284-1:20024 (see Section 2.1.3, Table 2.2).

For CEMs that monitor gases, the sample plane location must comply with therequirements given in Section 2.2.3.

In many applications the calibration of the CEM is established by comparison withsimultaneous measurements obtained using a standard periodic manual samplingmethod or an instrumental monitoring method. Wherever possible, such monitoringshould be undertaken in close proximity to the CEM and must comply with thesampling requirements in Section 2.1 or 2.2 as appropriate. Further information iscontained in BS EN 14181:20049.

3.2 CEMs measuring gas volumetric flow rates

The positional requirements for CEMs measuring gas volumetric flow rate arespecified in BS ISO 1416410, and these are summarised in Table 3.1. The flow-stability criteria are given in Table 3.2.

Table 3.1 Positional requirements for continuous gas-flow monitoring

General location of sampling plane Representative of total volume-flow in the ductLength of straight section At least ten hydraulic diameters long.

Note: this is more stringent than BS EN 13284-1:2002.Location of sampling plane in straightsection and in relation to bends fansand the like

At least five hydraulic diameters upstream and at least fivehydraulic diameters downstream from any flow disturbance.

Table 3.2 Flow-stability criteria for continuous gas-flow monitoringAngle of gas flow 10 from duct axis

Flow direction No local negative gas flow

Minimum velocity As specified by CEMs manufacturer

Gas velocity variations Must be 10% at any sample point

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4. Sampling facilities and safety requirements for stack-emissionmonitoring

4.1. Access and facilities for periodic monitoring

4.1.1 Safe working platform and means of access to the sampling position

Industrial processes are regulated by the Agency through authorisations or permitsissued under IPC or Pollution and Prevention Control (PPC) Regulations. These placerequirements on an operator to provide a safe and normally permanent means ofaccess to enable monitoring to be carried out at specified release points. However, inexceptional circumstances, for example, at an old installation where limited accessprevents the installation of a permanent platform, temporary structures (such as,scaffolding) may be used, provided it is fully justified by the operator.

All platforms, whether permanent or temporary, should meet the minimum weightcriteria required for sampling. This is defined as 400kg point load in BS EN 13284-1:2002 and for permanent platforms is achievable. However, temporary, scaffoldplatforms cannot be constructed to this specification and must, instead, be constructedto a specific minimum scafftag category of heavy duty or meet the requirementsstated in the monitoring standard, whichever is the greater. Temporary platforms mustalso be tied to, or supported by, a permanent structure. Sampling from mobile accessplatforms, cherry pickers or ladders is unacceptable. Sampling from roofs orthe tops of arrestment equipment, vessels and ducts is unacceptable unless they havebeen assessed as being suitable by meeting the requirements for platforms describedin this Note and the Work at Height Regulations 200511.

The platform and access must meet all current legislative requirements regardingdimensions and construction, be maintained to a safe standard and undergo regularinspection by a competent person. For scaffolding, a properly completed and datedScafftag is one means of demonstrating and recording this inspection. Forpermanently installed platforms, the structural integrity of the platform and anysupports and attachments shall be assessed periodically by the process operator. Theinspection shall also include the effects of weathering, corrosion and damage. Thefrequency and comprehensiveness of inspection shall be commensurate with the riskof failure and serious injury. For example, a steel platform at great height and in acorrosive atmosphere may require more frequent and thorough inspections than a lowplatform in a normal atmosphere. Records of inspections should be available for themonitoring team to check before they ascend to the work area.

The Work at Height Regulations place specific stipulations that require the employerto carry out inspections of work equipment and pre-use checks of places of work.

A permanent platform should be used where possible. If a temporary platform is required then the

process operator and sampling team must liase to ensure that the scaffold erected is of a sufficientstandard to support the minimum weight requirement. The sampling team leader should confirm thisbefore undertaking the work. Special or masonry independent tied scaffold would normally besufficient.

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Working platforms and associated guard rails, barriers, toe-boards, ladders etc, mustbe inspected at the following frequencies:

after assembly/installation but before use; at suitable intervals where there has been exposure to conditions causing

deterioration; and at each time an exceptional circumstance has occurred which is liable to

jeopardise its safety and within seven days prior to use if the platform is one fromwhich a person could fall more than 2m.

The platform shall be provided with handrails and kick-boards that meet therequirements of the Workplace (Health, Safety and Welfare) Regulations 1992,(Regulation 13) for permanent platforms and the Health and Safety in ConstructionRegulations (HS(G)150) for temporary platforms.

Where the selected sample plane is located in a horizontal section of a largerectangular duct, and where some of the sample points are positioned above aconvenient and safe working height (nominally 1.75m maximum for sample probehandling), it will be necessary to provide a dual-level sampling platform of adequatedesign so that sampling staff can carry out the full range of sampling requirements ina safe and satisfactory manner.

Note: performing monitoring in horizontal sections of very large circular ductspresents severe practical difficulties in obtaining access to all sample points. Suchsituations should be avoided.

Removable chains or self-closing gates shall be used at the platform to preventworkers falling through access hatches or ladders.

The platform shall have suitable weather protection for personnel and equipment. Theplatform shall not accumulate free-standing water and, if necessary, drainage is to beprovided.

BS EN 13284-1:20024 contains requirements related to the working platform. Thereare also a number of CEN standards covering platforms and access12, 13, 14, 15.

4.1.2 Space for the equipment and personnel

The space/size requirements for platforms are shown in Figures 4.1 to 4.4. Theplatform surface area should not be less than 5m2. The minimum width at any pointshall be 2m. The minimum length in front of the access port shall be 2m or the lengthof the probe (including nozzles, suction/support tubes and associated filter holders)plus 1m (whichever is the greater). The platform should be wide enough to preventsampling equipment extending beyond the platform.

4.1.3 Means of entry into the stack (sampling access ports)

The access ports shall be big enough for the insertion and removal of the equipmentused and to allow the sampling points to be reached. BS EN 13284-1:20024recommends that access ports have a minimum diameter of 125mm (illustrated in

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Figure 4.5) or a surface area of 100mm x 250mm, except on stacks smaller than 0.7mdiameter. For small stacks (less than 0.7m diameter) a smaller socket (for example50mm (2-inch) nominal BSP) may be necessary, but there must be close liaison withthe sampling team to ensure the required probes and Pitots can be accommodated.

The port socket shall not project into the gas stream (see Figure 4.5). Typicalarrangements of access fitments are shown in Figures 4.6 and 4.7. The operator mustmaintain the ports in good condition and free them up prior to work being undertaken.

The UK standard type of sampling port is a 4-inch nominal British Standard pipe (BSP) socket.

The aim is to simplify the insertion of an in-line 47mm filter holder, which is approximately 150mm

long.

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Figure 4.1 Typical area required behind probe for handling

Figure 4.2 Plan view of platform working area and orientation recommendationsfor small vertical circular stacks (

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Figure 4.3 Plan and side view of platform working area and orientationrecommendations for large vertical circular stacks (3.6m diameter)

Platform

Stack

'L'L (Length) = Probe length +1m

Minimum width of platform atany point is 2m

Probe length = stack diameter / 2

PROVISION FORLIFTING EQUIPMENT

MONORAIL SUPPORTS

Sampling should be carried out fromfour sample holes on these large stacks

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Figure 4.4 Plan view of recommended platform working area for square orrectangular ducts (up to l1 = 3.6 m)

Depth of platform (a) = Probe length +1m

Duct side length, l1 (m) 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0Duct side width, w (m) 0.6 8.0 1.0 1.2 1.4 1.6 1.8 2.0Width of platform, b (m) 2.0 2.0 2.0 2.0 2.0 2.0 2.1 2.2

Duct side length, l1 (m) 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6Duct side width, w (m) 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6Width of platform, b (m) 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3.0

Figure 4.5 Standard 125mm access port

STACK WALL

1

2

4

3

129.30

1. Flange BS10 125mm (5)

2. Pipe stub 125mm schedule 40

3. Pipe stub length should be a minimum of 75mm from the stack wall (recommended is 100mm)

4. Recommendation that 1000mm of Unistrut P1000 is fitted vertically on the centre line of thesample port for positioning of the monorail

Duct Samplingplatform

l1

w b

a

Minimum platform area (a xb) shall be 5m2

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Figure 4.6 Typical arrangement of access fittings on large circular stacks (3.6mdiameter)

Note - for small circular stacks, two ports at 90 will usually suffice.

90Centre line

Parallel-sided socket


Plan view


Side elevation

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Figure 4.7 Typical arrangement of access fittings on large square/rectangularstacks

Sampling centre line



Plan view

Side elevation


Note - for small stacks, ports on one side will usually suffice.

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4.1.4 Essential services

The sampling position should have artificial lighting or have facilities for temporarylighting. The sampling position should be well ventilated. Single phase 110 Velectrical power of a suitable current shall be provided by a suitable number ofoutdoor waterproof sockets at the platform. Water, drainage and compressed air shallbe supplied at the request of the sampling team. When undertaking sampling of gasesusing instrumental techniques, many monitoring organisations use mobile emissionsmonitoring laboratories, which may require a 32amp or even a 63amp power supply.When this type of sampling is undertaken operators need to provide parking facilitiesfor these vehicles within close proximity to the sampling location.

Lifting equipment is required for the raising and lowering of apparatus where accessto the sampling platform is by vertical, or steeply inclined, ladders or stairs. In allsuch cases, the lifting equipment (for example, hoists) and attachments (for example,eyes) must be installed, inspected and maintained by the site operator.

A sampling monorail should be attached above the sampling ports to enable certaindesigns of sampling train to be suspended.

4.1.5 Other issues

The platform shall be, as far as, possible free from obstructions that would hampersampling.

Protection from adverse weather will usually be required for an outdoor samplingposition.

An additional access port to vent sample air back into the duct may be necessary if theflue gas presents an exposure hazard.

4.2 Access and facilities for periodic monitoring of gases

Access and facilities requirements for gases alone are usually less demanding than forparticulates. In practice, meeting the requirements for particulates in Section 4.1 willalso satisfy the requirements for gases. When gas concentrations only are to bemonitored, smaller access ports than those specified for particulates may bepermissible following consultation and agreement with the sampling team.

4.3 Access and facilities for CEMs

The requirement for access and facilities will be dependent on:

whether the CEM requires calibration by periodic monitoring using a standardmethod;

the need for routine maintenance and operational function checks (such as spanand zero checks).

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If the CEM requires calibration by periodic monitoring, then the access and facilitiesshould as a minimum comply with the requirements given in Section 4.1 and 4.2, forparticulates and gases respectively. Routine maintenance and calibration maynecessitate additional access and facilities.

If the CEM is calibrated by a means other than periodic monitoring, then the accessand facilities required will be solely those needed for the maintenance and calibrationactivities. Such activities will vary from one CEM to another. In practice, however,it is unlikely that the standard of access and facilities will be less than that specified inSection 4.1. The latter should be the default requirement, with any relaxation needingcareful assessment and justification.

The CEN standard which covers quality assurance of CEMs, BS EN 14181:20049,requires good access to the CEM to allow frequent inspection and to minimise thetime needed for calibration tests. The standard reiterates many of the specificrequirements given in Section 4.1.

4.4 The risk-management approach to site work

4.4.1 Safety has the highest priority

Safety must be considered at the earliest point in the monitoring strategy, and must berevisited whenever a decision is made on sampling positions, access andrequirements. Any change to the sampling positions, access and requirements issubject to the overriding requirement for the work to be carried out safely forexample, a modification to the sampling position that would theoretically provide atechnical improvement must not proceed if it introduces an unacceptable safety risk.

There are many hazards associated with stack monitoring. The basic principles ofhealth and safety must be applied. In particular, a risk assessment must be carried outbefore starting work - this is a legal requirement. The risk assessment should bedocumented. Risk Assessments should also be performed during the site reviewprocess. Further guidance is available in the MCERTS Performance Standard forOrganisations1.

The risk assessment will assess the level of risk from each of the various hazardspresent. If the risk is unacceptable, control measures must be used to reduce the riskto an acceptable level before starting work. It is recommended that, as a minimum,the routine hazards described in Section 4.4.6 of this TGN should be included in therisk assessment. However, there may be other hazards - every site is different. Thereader is advised to consult the Source Testing Associations (STA) booklet RiskAssessment Guide: Industrial-emission Monitoring16 which is updated frequently.

The focus of this section is on periodic monitoring, as this approach requires aconsiderable amount of manual work on-site. However, the principles apply equallywhen using CEMs and should be followed whenever manual work on CEMs iscarried out, for example, during installation, maintenance and calibration.

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4.4.2 Prominent hazards encountered when stack-emission monitoring

The most prominent hazards are shown in Figure 4.8. It must be reiterated that this isnot an exhaustive list and there may be other hazards. Every site is different.

Figure 4.8 Most prominent hazards associated with stack monitoring

4.4.3 The risk-assessment process

The fundamental stages of the risk-assessment process can be summarised as:

Step 1Identify theHAZARDS

Step 3Apply CONTROLMEASURES

Step 2Assess the RISKS

RISK TOHEALTH &

SAFETY

General sitehazards

Weather,environmentand welfare

Site trafficFire andemergency

Physicalhazards at stack

Chemicalhazards at stack

Compressed gases

Sunburn

Temperatureextremes

Wind, rain,lightning, snowand ice

Mechanicaloperations

Chemicaloperations

Lifting

Falling

Electricity

Chemicalhazards in lab

Exposure tosubstances fromflue gases

Exposure tosubstances used inmonitoring tests

Exposure tosubstances used inanalysis andcleaning

Lone working

Burns

Tiredness

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Because the risk assessment forms the foundation of safe working on stacks, it is veryimportant to understand the distinction between hazard and risk. These terms aredefined in Box 4.1.

Using an extreme example to illustrate this difference between hazard and risk,working on stacks is associated with the hazard of slips on icy platforms. The risk ofslipping is high on a cold winters day, but is very low in summer.

The first step of the risk assessment is therefore to identify the hazards that will befaced. Then, a judgement must be made on what the risk will be (that is, thelikelihood of an accident) in the light of all the relevant factors. If the risk is notacceptable*, then control measures must be put in place to reduce the risk. Only thenshould work commence. Control measures can be:

engineering - for example, a self-closing gate to reduce the risk of falls from theplatform;

procedural - for example, permit-to-work systems; personal protective equipment (PPE) - for example, safety goggles to reduce the

risk of eye injury when opening access ports.

For many hazards, there will be a choice of control measures. PPE measures shouldbe used to reduce the risk further only when other measures fail to reduce the risk toas low as reasonably practicable. PPE shall not be the control measure of first choice.

4.4.4 Responsibilities

The Management of Health and Safety at Work Regulations 1999 has manyrequirements. Specifically, it places a duty of care on employers to:

ensure the competency of employees through training and experience to allowthem to work in a safe manner;

adequately assess the health and safety risks of employees and any other personsnot in his employment who may be affected by the works;

identify and implement appropriate risk-control measures to ensure the safety ofemployees and other persons;

review risks and control measures regularly to ensure continued validity.

* The criterion for the risk being acceptable is that the risk shall be as low as is reasonably

practicable, commonly known by the abbreviation ALARP.

Box 4.1 The distinction between hazard and risk Hazard - a substance or physical situation with inherent potential to cause harm Risk - an estimation of the likelihood of that potential being realised, within a

specified period or in specified circumstances, and the consequence

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For operators carrying out stack-emissions monitoring using their own staff, theresponsibility for the risk assessment and safe systems of work is straightforward.Where operators contract-out the monitoring, both the operator and monitoringcontractor have the responsibility as site occupier and employer to follow safesystems of work.

The operator also has a responsibility to employ competent monitoring organisationsand the monitoring organisation has a responsibility to ensure employees arecompetent to carry out the work safely.

Where work is being carried out by a monitoring organisation directly for theEnvironment Agency, the monitoring organisation, the operator and the regulator allhave responsibilities in this regard. In practice, the monitoring team is usually bestplaced to carry out a comprehensive risk assessment of the work they carry out onsite. Since they are also usually subject to the greatest risk, the site team shouldalways carry out their own risk assessment, regardless of whether the operator hasdone so.

4.4.5 When to carry out a risk assessment

Where a monitoring organisation has not previously carried out sampling from aparticular stack, a site review will be necessary to:

carry out a risk assessment; assess the suitability of the sampling position; deal with practical issues to ensure subsequent monitoring proceeds smoothly (for

example, suitability of equipment, length of Pitots and probes required).

It is very important to understand that all safety improvements and control measuresmust be in place before the monitoring team starts work. For this reason, a riskassessment carried out as part of a site review before the monitoring visit ispreferable, as this gives the site operator time to implement any control measuresfound to be necessary.

Where the monitoring organisation has carried out sampling at the site on previousoccasions, a full site review may not be necessary. However, the monitoring teammust still carry out a risk assessment before they start sampling work. It is importantthat this risk assessment is carried out at the start of every monitoring campaign at asite, even if the team has been before. This is a good discipline because it focuses theteams attention on safety as the first issue to address on-site. It also reduces thepossibility of the staff becoming complacent after several visits because they feel theyknow all the issues.

4.4.6 Getting the operator involved

When the monitoring team arrives on-site, its first task must be to conduct the risk-assessment. If the team has not worked on the site before, the operatorsrepresentative should accompany them as they make the assessment for reasons ofsafety and to provide knowledge of specialised site-specific issues (for example,

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process conditions, escape routes). It is not always necessary for the team to beaccompanied during the risk assessment when they return for repeat visits.

However, whether it is the teams first visit to the site or a repeat visit, the operatorsrepresentative should be briefed on the findings of the completed risk assessment.This will give the operator the opportunity to raise any additional issues of concern,and comment on the findings of the assessment and the control measures themonitoring team has decided will be necessary. If the operator has any relevantcomments, these should be considered. They can be incorporated into the assessmentand its findings if they reduce the risk further, but not if they hinder the reduction ofrisk.

Some of the control measures required may need to be put in place by the operator.The operators confirmation that these have been completed should be obtainedbefore monitoring work is started.When the site work is finished, any relevant comments should be noted on the riskassessment based on any lessons learnt. This will be useful for the next visit.

4.4.7 Reporting accidents and near misses

There is a statutory requirement to report certain accidents under the Reporting ofInjuries Diseases and Dangerous Occurrences Regulations (RIDDOR) 1995. Anyincidents coming under these criteria must be reported to the Health and SafetyExecutive. However, there are additional benefits to be gained from informingrelevant organisations such as the STA and the Environment Agency about suchevents as well as other, non-reportable, accidents or near misses. Though some of theoccurrences may be minor, knowledge about them aids the development ofprocedures and guidance to avoid future accidents.

The STA produces guidance for its members on safe working procedures for stackmonitoring. This is regularly revised and updated, taking into account legislativechanges and lessons learned from incidents and near misses. The STA also has a fast-track system for disseminating urgent safety information to members. To enable theSTA to give maximum value to its members, it asks monitoring teams and operatorsto submit details of incidents and near-misses. These submissions are treated in thestrictest confidence and can, if desired, be made anonymously.

The Environment Agency has its own reporting procedure for accidents, damage,environmental impact and near misses involving its own staff, and/or monitoringteams working under direct contract to the Environment Agency. The EnvironmentAgency passes details of all generic safety incidents and resultant lessons learned tothe STA to allow the source testing industry to benefit from this information. Theinformation passed to the STA does not contain details on the sites or the monitoringteams involved.

4.4.8 Further guidance

Box 4.2 shows some of the major items of legislation and guidance relevant to thehazards depicted in Figure 4.8. The STA has produced a health and safety booklet15,which describes each of the most prominent hazards and the factors that affect the risk

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of an accident from them. This guidance, together with other relevant guidance,should be consulted as part of the risk assessment process. However, safetymanagement is a fast-evolving subject and new guidance, and new and revisedlegislation appears frequently. All parties involved in stack-emission monitoringshould ensure they take account of the most recent developments.

5. Status of this document

5.1 Version 3 of TGN M1 replaces version 2, which is withdrawn and should bediscarded.

5.2 Version 3 may be subject to review and amendment following publication. Forthe latest version go to the Environment Agencys website at :

www.environment-agency.gov.uk and put M1 into the Search facility.

Box 4.2 Legislation and guidance relevant to stack-emission monitoringhealth and safetyLegislation Electricity at Work Regulations 1989 Personal Protective Equipment at Work Regulations 1992 Workplace (Health, Safety and Welfare) Regulations 1992 The Carriage of Dangerous Goods (Classification, Packaging and Labelling) and Use of

Transportable Pressure Receptacles Regulations, 2004 The Lifting Operations and Lifting Equipment Regulations 1998 (LOLER) Control of Substances Hazardous to Health Regulations 1999 (COSHH) Management of Health and Safety at Work Regulations 1999 Noise at Work Regulations 1989 Construction Health and Welfare Regulations 1996 Manual Handling Operations Regulations 1998 Confined Spaces Regulations 1999 Work at Height Regulations 2005

Guidance HS(G)150, Health and Safety in Construction: guidance on small lifting equipment HS(G)107, Maintaining portable and transportable electrical equipment HSE guidance leaflet INDG308 5/00 C1200, The Safe Use of Gas Cylinders HSE information leaflet IND(G)147(L), Keep Your Top On Health Risks from Working in

the Sun HSE Guidance, 5 Steps to Risk Assessment HSE Guidance, A Guide to Risk Assessment Requirements HSC Safe work in confined spaces BS4211 Specification for ladders for access to chimneys, other high structures, silos and bins STA Health Safety Guidance Note HSGN0008, Hazards, Risks and Risk Control in Stack

Testing Operations

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Annex 1 Sample point requirements as specified in ISO 9096:2003

Table 1 Minimum number of sampling points for circular stacksMinimum number ofsampling points perline,

Minimum number ofsampling points perplane,

Range of ductdiameters(m)

Minimumnumber ofsampling lines(diameters) Incl.

centrepoint

Excl.centrepoint

Incl.centrepoint

Excl.centrepoint

2.00 2 9 8 17 16a. Using only one sampling point can give rise to errors greater than those specified in ISO 9096:2003

Table 2 Minimum number of sampling points for rectangular stacksRange ofsampling planeareas (m2)

Minimum number of sidedivisions a

Minimum number of sampling pointsper plane

1.50 4 16Note a: Other side divisions may be necessary, for example, if the longest stack side length is more than twicethe length of the shortest side (see Figure 2.4). Sample lines for square and rectangular stacks are explained inSection 2.1.8.2Note b: Using only one sampling point can give rise to errors greater than those specified in ISO 9096:2003

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References

1. MCERTS, Manual stack-emission monitoring: performance standard fororganisations, Version 4, September 2003. Environment Agency.

2. MCERTS, Manual-stack emission monitoring: personnel competency standard,Version 3, July 2005, Environment Agency.

3. Technical Guidance Note M2 Monitoring of Stack Emissions to Air, Version 3.1, June2005 Environment Agency.

4. BS EN 13824:2002 Stationary source emissions Determination of low range massconcentration of dust Part 1 Manual gravimetric method..

5. BS ISO 9096:2003 Stationary source emissions Manual determination of massconcentration of particulate matter.

6. Quality Guidance Note QGN001 r1, Guidance on Assessing MeasurementUncertainty in Stack Monitoring, Source Testing Association, September 2004.

7. ISO 10780:1994, Stationary source emissions Measurement of velocity and volumeflowrate of gas streams in ducts.

8. ISO 10396: 1993, Stationary source emissions Sampling for the automateddetermination of gas concentrations.

9. BS EN 14181:2004. Stationary source emissions Quality assurance of automatedmeasuring systems.

10. BS ISO 14164: 1999, Stationary source emissions Determination of the volumeflowrate of gas streams in ducts Automated method.

11. Work at Height Regulations 2005. Statutary Instrument No. 735. ISBN 0 11 0725638.HMSO.

12. EN ISO 14122-1: 2001, Safety of machinery Permanent means of access tomachines and industrial plants Part 1: Choice of a fixed means of access betweentwo levels.

13. EN ISO 14122-2: 2001, Safety of machinery Permanent means of access tomachines and industrial plants Part 2: Working platforms and gangways.

14. EN ISO 14122-3: 2001, Safety of machinery Permanent means of access tomachines and industrial plants Part 3: Stairways, stepladders and guard-rails.

15. EN ISO 14122-4: 1996, Safety of machinery Permanent means of access tomachines and industrial plants Part 4: Fixed ladders.

16. Risk Assessment Guide: Industrial-emission Monitoring. Source Testing Association.www.S-T-A.org (updated frequently).

m1version3oct2005_1

Documents

sampling position

sampling particulates

sampling facilities

sampling technique

position of sampling

periodic sampling of

sampling points access

number of sampling points