YES, G.H.S. is more

than 16 items on a

SDS, 6 items on a

label and 9 new

pictogram

Practice Safety in the Use of Chemicals at Work is to protect workers from the

hazards of chemicals, to prevent or reduce the incidence of chemically- induced

illnesses and injuries resulting from the use of chemicals at work, and consequently

to enhance the protection of the general public and the environment by providing

guidelines for:

� ensuring that all chemicals for use at work—including impurities, by-products and

intermediates, and wastes that may be formed—are evaluated to determine their

hazards

� ensuring that employers are provided with a mechanism for obtaining from their

suppliers information about the chemicals used at work to enable them to implement

effective programs to protect workers from chemical hazards

� providing workers with information about the chemicals at their workplaces and

about appropriate preventive measures to enable them to participate effectively in

safety programs

� establishing principles for such programs to ensure that chemicals are used safely

� making special provision to protect confidential information, the disclosure of

which to a competitor would be liable to cause harm to an employer’s business, so

long as the safety and health of workers are not compromised thereby.

The major focus of such measures which provide for safety of workers are, in

particular:

� the production and handling of hazardous chemicals

� the storage of hazardous chemicals

� the transport of hazardous chemicals, consistent with national or international

transport regulations

� the disposal and treatment of hazardous chemicals and hazardous waste products,

consistent with national or international regulations.

There are various means by which the competent authority may achieve this aim. It

may enact national laws and regulations; adopt, approve or recognize existing

standards, codes or guidelines; and, where such standards, codes or guidelines do

not exist, an authority may encourage their adoption by another authority, which can

then be recognized. The governmental agency may also require that employers

justify the criteria by which they are working.

When workers are potentially exposed to chemicals that are hazardous to health,

they must be safeguarded against the risk of injury or disease from these chemicals.

There should be no exposure which exceeds exposure limits or other exposure

criteria for the evaluation and control of the working environment established by the

competent authority, or by a body approved or recognized by the competent

authority in accordance with national or international standards.

Control measures to provide protection for workers could be any combination of the

following:

1. good design and installation practice:

� totally enclosed process and handling systems

� segregation of the hazardous process from the operators or from other processes

2. plants processes or work systems which minimize generation of, or suppress or

contain, hazardous dust, fumes, etc., and which limit the area of contamination in

the event of spills and leaks:

� partial enclosure, with local exhaust ventilation (LEV)

� LEV

� sufficient general ventilation

3. work systems and practices:

� reduction of the numbers of workers exposed and exclusion of non-essential access

� reduction in the period of exposure to workers

� regular cleaning of contaminated walls, surfaces, etc.

� use and proper maintenance of engineering control measures

� provision of means for safe storage and disposal of chemicals hazardous to health

4. personal protection (where the above measures do not suffice, suitable PPE

should be provided until such time as the risk is eliminated or minimized to a level

that would not pose a threat to health)

5. prohibition of eating, chewing, drinking and smoking in contaminated areas

6. provision of adequate facilities for washing, changing and storage of clothing,

including arrangements for laundering contaminated clothing

7. use of signs and notices

8. adequate arrangements in the event of an emergency.

Chemicals known to have carcinogenic, mutagenic or teratogenic health effects

should be kept under strict control.

Record Keeping

Record keeping is an essential element of the work practices which provide a safe

use of chemicals. Records should be kept by employers on measurements of

airborne hazardous chemicals.

� Personal sampling measurements, including the exposures calculated, should be

recorded.

� The workers and their representatives, and the competent authority, should have

access to these records.

Besides the numerical results of measurements, the monitoring data should include,

for example:

� the marking of the hazardous chemical

� the location, nature, dimensions and other distinctive features of the workplace

where static measurements were made; the exact location at which personal

monitoring measurements were made, and the names and job titles of the workers

involved

� the source or sources of airborne emissions, their location and the type of work and

operations being performed during sampling

� relevant information on the functioning of the process, engineering controls,

ventilation and weather conditions with respect to the emissions

� the sampling instrument used, its accessories and the method of analysis

� the date and exact time of sampling

� the duration of the workers’ exposure, the use or non-use of respiratory protection

and other comments relating to the exposure evaluation

� the names of the persons responsible for the sampling and for the analytical

determinations.

Records should be kept for a specified period of time determined by the competent

authority.

Information and Training

Correct instruction and quality training are essential components of a successful

hazard communication program.

These include the following:

� Workers should be informed of the hazards associated with chemicals used at their

workplace.

� Workers should be instructed about how to obtain and use the information provided

on labels and chemical safety data sheets.

� Workers should be trained in the correct and effective use of the control measures,

in particular the engineering control measures and measures for personal protection

provided, and should be made aware of their significance.

� Employers should use chemical safety data sheets, along with information specific

to the workplace, as a basis for the preparation of instruction to workers, which

should be in writing if appropriate.

� Workers should be trained on a continuing basis in the working systems and

practices to be followed and their significance for safety in the use of chemicals at

work, and in how to deal with emergencies.

The review should include the examination of:

� whether workers understand when protective equipment is required, and its

limitations

� whether workers understand the most effective use of the engineering control

measures provided

� whether workers are familiar with procedures in the event of an emergency

involving a hazardous chemical

� procedures for the exchange of information between shift workers.

Classification systems

The competent authority, or a body approved or

recognised by the competent authority, should

establish systems and specific criteria for classifying

a chemical as hazardous and should progressively

extend these systems and their application. Existing

criteria for classification established by other

competent authorities or by international agreement

may be followed, if they are consistent with the

criteria and methods outlined in this code, and this is

encouraged where it may assist uniformity of

approach.

Suppliers should ensure that chemicals they supplied

have been classified or that they have been identified

and their properties assessed .

Manufacturers or importers, unless exempted, should

give to the competent authority information about chemical elements and

compounds not yet included in the consolidated classification list compiled by the

competent authority, prior to their use at work (assessment of new chemicals)).

The limited quantities of a new chemical required for research and development

purposes may be produced by, handled in, and transported between laboratories and

pilot plant before all hazards of this chemical are known in accordance with national

laws and regulations. All available information found in literature or known to the

employer from his or her experience with similar chemicals and applications should

be fully taken into account, and adequate protection measures should be applied, as

if the chemical were hazardous. The workers involved must be informed about the

actual hazard information as it becomes known.

Criteria for classification

The criteria for the classification of chemicals should be based upon their intrinsic

health and physical hazards, including:

(a) toxic properties, including both acute and chronic health effects in all parts of

the body;

(b) chemical or physical characteristics, including flammable, explosive, oxidising

and dangerously reactive properties;

(c) corrosive and irritant properties;

(d) allergenic and sensitising effects;

(e) carcinogenic effects;

(f) teratogenic and mutagenic effects;

(g) effects on the reproductive system.

Method of classification

The classification of chemicals should be based on available sources of information,

e.g.:

(a) test data;

(b) information provided by the manufacturer or importer, including information on

research work done;

(c) information available as a result of international transport rules, e.g., the United

Nations Recommendations on the Transport of Dangerous Goods, which should be

taken into account for the classification of chemicals in the case of transport and

which should be taken into account in respect of hazardous wastes;

(d) reference books or literature;

(e) practical experience;

(f) in the case of mixtures, either on the test of the mixture or on the known hazards

of their components;

Hazard classification and labelling systems are included in legislation covering the

safe production, transport, use and disposal of chemicals. These classifications are

designed to provide a systematic and comprehensible transfer of health information.

Only a small number of significant classification and labelling systems exist at the

national, regional and international levels. Classification criteria and their definitions

used in these systems vary in the number and degree of hazard scales, specific

terminology and test methods, and the methodology for classifying mixtures of

chemicals. The establishment of an international structure for harmonizing

classification and labelling systems for chemicals would have a beneficial impact on

chemical trade, on the exchange of information related to chemicals, on the cost of

risk assessment and management of chemicals, and ultimately on the protection of

workers, the general public and the environment.

The major basis for classification of chemicals is the assessment of exposure levels

and environmental impact (water, air and soil). About half of the international

systems contain criteria related to a chemical’s production volume or the effects of

pollutant emissions. The most widespread criteria used in chemical classification

are values of median lethal dose (LD50) and median lethal concentration (LC50). These

values are evaluated in laboratory animals via three main pathways—oral, dermal

and inhalation—with a one-time exposure. Values of LD50 and LC50 are evaluated in

the same animal species and with the same exposure routes. The Republic of Korea

considers LD50 with intravenous and intracutaneous administration as well. In

Switzerland and Yugoslavia chemical management legislation requires quantitative

criteria for LD50 with oral administration and adds a provision which specifies the

possibility of different hazard classifications based on the route of exposure.

The UN classification subdivides chemicals into nine classes of hazards:

� 1st class—explosive substances

� 2nd class—compressed, liquefied, dissolved under pressure or deeply condensed

gases

� 3rd class—easily inflammable liquids

� 4th class—easily inflammable solid substances

� 5th class—oxidizing substances, organic peroxides

� 6th class—poisonous (toxic) and infectious substances

� 7th class—radioactive substances

� 8th class—corrosive agents

� 9th class—other dangerous substances.

The packaging of goods for the purpose of transport, an area specified by the

UNRTDG, is not covered as comprehensively by other systems.

Labelling

Labels on containers of hazardous chemicals provide the first alert that a chemical

is hazardous, and should provide basic information about safe handling procedures,

protective measures, emergency first aid and the chemical’s hazards. The label

should also include the identity of the hazardous chemical(s) and the name and

address of the chemical manufacturer.

Labelling consists of phrases as well as graphic and colour symbols applied directly

on the product, package, label or tag. The marking should be clear, easily

comprehensible and able to withstand adverse climatic conditions. The labelling

should be placed against a background that contrasts with the product’s

accompanying data or package colour. The SDS provides more detailed information

on the nature of the chemical product’s hazards and the appropriate safety

instructions.

Before a new hazardous substance is received for storage, information concerning

its correct handling should be provided to all users. Planning and maintaining of

storage areas are necessary to avoid material losses, accidents and disasters. Good

housekeeping is essential, and special attention should be paid to incompatible

substances, suitable location of products and climatic conditions.

Written instructions of storage practices should be provided, and the chemicals’

material safety data sheets (SDSs) should be available in storage areas. Locations of

the different classes of chemicals should be illustrated in a storage map and in a

chemical register. The register should contain the maximum allowed quantity of all

chemical products and the maximum allowed quantity of all chemical products per

class. All substances should be received at a central location for distribution to the

storerooms, stockrooms and laboratories. A central receiving area is also helpful in

monitoring substances that may eventually enter the waste-disposal system. An

inventory of substances contained in the storerooms and stockrooms will give an

indication of the quantity and nature of substances targeted for future disposal.

Stored chemicals should be examined periodically, at least annually. Chemicals with

expired shelf lives and deteriorated or leaking containers should be disposed of

safely. A “first in, first out” system of keeping stock should be used.

The storage of dangerous substances should be supervised by a competent, trained

person. All workers required to enter storage areas should be fully trained in

appropriate safe work practices, and a periodic inspection of all storage areas

should be carried out by a safety officer. A fire alarm should be situated in or near

the outside of the storage premises. It is recommended that persons should not work

alone in a storage area containing toxic substances. Chemical storage areas should

be located away from process areas, occupied buildings and other storage areas. In

addition, they should not be in proximity of fixed sources of ignition.

Provincial Legislation

Detailed legislation has been drawn up in many countries to regulate the manner in

which various dangerous substances may be stored; this legislation includes the

following specifications:

� type of building, its location, the maximum amounts of various substances that may

be stored in one place

� type of ventilation required

� precautions to be taken against fire, explosion and the release of dangerous

substances

� type of lighting (e.g., flameproof electrical equipment and light fixtures when

explosive or flammable materials are stored)

� number and location of fire exits

� security measures against entry by unauthorized persons and against theft

� labelling and marking of storage vessels and pipelines

� warning notices to workers as to the precautions to be observed.

LABORATORY HYGIENE

Setting up a Safe and Healthy Laboratory

Occupational exposure to hazardous chemicals in laboratories

Ventilation

(a) General laboratory ventilation. This system should: Provide a source of air for

breathing and for input to local ventilation devices; it should not be relied on for

protection from toxic substances released into the laboratory; ensure that

laboratory air is continually replaced, preventing increase of air concentrations of

toxic substances during the working day; direct air flow into the laboratory from

non-laboratory areas and out to the exterior of the building.

(b) Hoods. A laboratory hood with 2.5 linear feet (76 cm) of hood space per person

should be provided for every 2 workers if they spend most of their time working with

chemicals; each hood should have a continuous monitoring device to allow

convenient confirmation of adequate hood performance before use. If this is not

possible, work with substances of unknown toxicity should be avoided or other

types of local ventilation devices should be provided.

(c) Other local ventilation devices. Ventilated storage cabinets, canopy hoods,

snorkels, etc. should be provided as needed. Each canopy hood and snorkel should

have a separate exhaust duct.

(d) Special ventilation areas. Exhaust air from glove boxes and isolation rooms

should be passed through scrubbers or other treatment before release into the

regular exhaust system. Cold rooms and warm rooms should have provisions for

rapid escape and for escape in the event of electrical failure.

(e) Modifications. Any alteration of the ventilation system should be made only if

thorough testing indicates that worker protection from airborne toxic substances

will continue to be adequate.

(f) Performance. Rate: 4-12 room air changes/hour is normally adequate general

ventilation if local exhaust systems such as hoods are used as the primary method

of control.

(g) Quality. General air flow should not be turbulent and should be relatively uniform

throughout the laboratory, with no high velocity or static areas; airflow into and

within the hood should not be excessively turbulent; hood face velocity should be

adequate (typically 60-100 lf/min) (152-254 cm/min).

(h) Evaluation. Quality and quantity of ventilation should be evaluated on

installation, regularly monitored (at least every 3 months), and reevaluated

whenever a change in local ventilation is made.

A laboratory can only be safe and hygienic if the work practices and procedures that

are followed there are safe and hygienic. Such practices are fostered by first giving

responsibility and authority for laboratory safety and chemical hygiene to a

laboratory safety officer who, together with a safety committee of laboratory

personnel, decides what tasks must be accomplished and assigns responsibility for

carrying out each of them.

The safety committee’s specific tasks include conducting periodic laboratory

inspections and summarizing the results in a report submitted to the laboratory

safety officer. These inspections are properly done with a checklist. Another

important aspect of safety management is periodic inspections of safety equipment

to ensure that all equipment is in good working order and in designated locations.

Before this can be done, an annual inventory of all the safety equipment must be

made; this includes a brief description, including size or capacity and manufacturer.

Of no less importance is a semiannual inventory of all laboratory chemicals,

including proprietary products. These should be classified into groups of chemically

similar substances and also classified according to their fire hazard. Another

essential safety classification depends on the degree of hazard associated with a

substance, since the treatment a substance receives is directly related to the harm

it can cause and the ease with which the harm is unleashed. Each chemical is put

into one of three hazard classes chosen on the basis of grouping according to the

order of magnitude of risk involved; they are:

1. ordinary hazard substances

2. high-hazard substances

3. extremely hazardous materials.

Ordinary hazard substances are those that are relatively easily controlled, are

familiar to laboratory personnel and present no unusual risk. This class ranges from

innocuous substances such as sodium bicarbonate and sucrose to concentrated

sulphuric acid, ethylene glycol and pentane.

High-hazard substances present much greater hazards than ordinary hazards. They

require special handling or, sometimes, monitoring, and present high fire or

explosion hazards or severe health risks. In this group are chemicals that form

unstable explosive compounds on standing (e.g., hydroperoxides formed by ethers)

or substances that have high acute toxicities (e.g., sodium fluoride, which has an

oral toxicity of 57 mg/kg in mice), or that have chronic toxicities such as

carcinogens, mutagens or teratogens. Substances in this group often have the same

kind of hazard as those in the group that follows. The difference is one of degree—

those in group 3, the extremely hazardous materials, have either a greater intensity

of hazard, or their order of magnitude is much greater, or the dire effects can be

released far more easily.

Extremely hazardous materials, when not handled correctly, can very readily cause a

serious accident resulting in severe injury, loss of life or extensive property damage.

Extreme caution must be exercised in dealing with these substances. Examples of

this class are nickel tetracarbonyl (a volatile, extremely poisonous liquid, the

vapours of which have been lethal in concentrations as low as 1 ppm) and

triethylaluminium (a liquid that spontaneously ignites on exposure to air and reacts

explosively with water).

One of the most important of the safety committee’s tasks is to write a

comprehensive document for the laboratory, a laboratory safety and chemical

hygiene plan, that fully describes its safety policy and standard procedures for

carrying out laboratory operations and fulfilling regulatory obligations; these include

guidelines for working with substances that may fall into any of the three hazard

categories, inspecting safety equipment, responding to a chemical spill, chemical

waste policy, standards for laboratory air quality and any recordkeeping required by

regulatory standards. The laboratory safety and chemical hygiene plan must be kept

in the laboratory or must be otherwise easily accessible to its workers. Other

sources of printed information include: chemical information sheets (also called

material safety data sheets, SDSs), a laboratory safety manual, toxicological

information and fire hazard information. The inventory of laboratory chemicals and

three associated derivative lists (classification of chemicals according to chemical

class, fire safety class and the three degrees of hazard) must also be kept with these

data.

Causes of Illness and Injury in the Laboratory

Measures for the prevention of personal injury, illness and anxiety are an integral

part of the plans for the day-to-day operation of a well-run laboratory. The people

who are affected by unsafe and unhygienic conditions in a laboratory include not

only those who work in that laboratory but also neighbouring personnel and those

who provide mechanical and custodial services. Since personal injuries in

laboratories stem largely from inappropriate contact between chemicals and people,

inappropriate mixing of chemicals or inappropriate supply of energy to chemicals,

protecting health entails preventing such undesirable interactions. This, in turn,

means suitably confining chemicals, combining them properly and closely regulating

the energy supplied to them. The main kinds of personal injury in the laboratory are

poisoning, chemical burns and injury resulting from fires or explosions. Fires and

explosions are a source of thermal burns, lacerations, concussions and other severe

bodily harm.

Chemical attack on the body. Chemical attack takes place when poisons are

absorbed into the body and interfere with its normal function through disturbance of

metabolism or other mechanisms. Chemical burns, or the gross destruction of tissue,

usually occur by contact with either strong acids or strong alkalis. Toxic materials

that have entered the body by absorption through the skin, eyes or mucous

membranes, by ingestion or by inhalation, can cause systemic poisoning, usually by

being spread via the circulatory system.

Poisoning is of two general types—acute and chronic. Acute poisoning is

characterized by ill effects appearing during or directly after a single exposure to a

toxic substance. Chronic poisoning becomes evident only after the passage of time,

which may take weeks, months, years or even decades. Chronic poisoning is said to

occur when each of these conditions is met: the victim must have been subjected to

multiple exposures over long periods of time and to metabolically significant

amounts of a chronic poison.

Chemical burns, usually encountered when liquid corrosives are spilled or splashed

on the skin or in the eyes, also occur when those tissues come in contact with

corrosive solids, ranging in size from powdery dusts to fairly large crystals, or with

corrosive liquids dispersed in the air as mists, or with such corrosive gases as

hydrogen chloride. The bronchial tubes, lungs, tongue, throat and epiglottis can also

be attacked by corrosive chemicals in either the gaseous, liquid or solid states.

Toxic chemicals also, of course, may be introduced into the body in any of these

three physical states, or in the form of dusts or mists.

Injury through fires or explosions. Both fires or explosions may produce thermal

burns. Some of the injuries caused by explosions, however, are particularly

characteristic of them; they are injuries engendered either by the concussive force

of the detonation itself or by such of its effects as glass fragments hurled through

the air, causing loss of fingers or limbs in the first case, or skin lacerations or loss of

vision, in the second.

Laboratory injuries from other sources. A third class of injuries may be caused

neither by chemical attack nor by combustion. Rather they are produced by a

miscellany of all other sources—mechanical, electrical, high-energy light sources

(ultraviolet and lasers), thermal burns from hot surfaces, sudden explosive shattering

of screw-capped glass chemical containers from the unexpected build-up of high

internal gas pressures and lacerations from the sharp, jagged edges of newly broken

glass tubing. Among the most serious sources of injury of a mechanical origin are

tall, high-pressure gas cylinders tipping over and falling to the floor. Such episodes

can injure legs and feet; in addition, should the cylinder stem break during the fall,

the gas cylinder, propelled by the rapid, massive, uncontrolled escape of gas,

becomes a deadly, undirected missile, a potential source of greater, more

widespread harm.

Injury Prevention

Safety sessions and information dissemination. Injury prevention, dependent on

performance of laboratory operations in a safe and prudent manner, is, in turn,

dependent on laboratory workers being trained in correct laboratory methodology.

Although they have received some of this training in their undergraduate and

graduate education, it must be supplemented and reinforced by periodic laboratory

safety sessions. Such sessions, which should emphasize understanding the physical

and biological bases of safe laboratory practice, will enable laboratory workers to

reject questionable procedures easily and to select technically sound methods as a

matter of course. The sessions should also acquaint laboratory personnel with the

kinds of data needed to design safe procedures and with sources of such

information.

Workers must also be provided with ready access, from their work stations, to

pertinent safety and technical information. Such materials should include laboratory

safety manuals, chemical information sheets and toxicological and fire hazard

information.

Prevention of poisoning and chemical burns. Poisoning and chemical burns have a

common feature—the same four sites of entry or attack:

(1) skin,

(2) eyes,

(3) mouth to stomach to intestines and

(4) nose to bronchial tubes to lungs.

Prevention consists in making these sites inaccessible to poisonous or corrosive

substances. This is done by placing one or more physical barriers between the

person to be protected and the hazardous substance or by ensuring that the ambient

laboratory air is not contaminated. Procedures that use these methods include

working behind a safety shield or using a fume hood, or utilizing both methods. The

use of a glove box, of course, of itself affords a twofold protection. Minimization of

injury, should contamination of tissue occur, is accomplished by removing the toxic

or corrosive contaminant as quickly and completely as possible.

Incompatible Materials

Incompatible materials are a pair of substances that, on contact or mixing, produce

either a harmful or potentially harmful effect. The two members of an incompatible

pair may be either a pair of chemicals or a chemical and a material of construction

such as wood or steel. The mixing or contact of two incompatible materials leads

either to a chemical reaction or to a physical interaction that generates a large

amount of energy. Specific harmful or potentially harmful effects of these

combinations, which can ultimately lead to serious injury or damage to the health,

include liberation of large amounts of heat, fires, explosions, production of a

flammable gas or generation of a toxic gas. Since a fairly extensive variety of

substances is usually found in laboratories, the occurrence of incompatibles in them

is quite common and presents a threat to life and health if they are not handled

correctly.

Incompatible materials are seldom mixed intentionally. Most often, their mixing is

the result of a simultaneous accidental breaking of two adjacent containers.

Sometimes it is the effect of leakage or dripping, or results from the mixing of gases

or vapours from nearby bottles. Although in many cases in which a pair of

incompatibles is mixed, the harmful effect is easily observed, in at least one

instance, a not readily detectable chronic poison is formed. This occurs as the result

of the reaction of formaldehyde gas from 37% formalin with hydrogen chloride that

has escaped from concentrated hydrochloric acid to form the potent carcinogen

bis(chloromethyl) ether. Other instances of not immediately detectable effects are

the generation of odourless, flammable gases.

Keeping incompatibles from mixing through the simultaneous breaking of adjacent

containers or through escape of vapours from nearby bottles is simple—the

containers are moved far apart. The incompatible pair, however, must first be

identified; not all such identifications are simple or obvious. To minimize the

possibility of overlooking an incompatible pair, a compendium of incompatibles

should be consulted and scanned occasionally to acquire an acquaintance with less

familiar examples. Preventing a chemical from coming in contact with incompatible

shelving material, through dripping or through a bottle breaking, is done by keeping

the bottle in a glass tray of sufficient capacity to hold all of its contents.

Occupational health professionals have generally relied on the following hierarchy of

control techniques to eliminate or minimize worker exposures: substitution,

isolation, ventilation, work practices, personal protective clothing and equipment.

Usually a combination of two or more of these techniques is applied. Although this

article focuses primarily on the application of ventilation techniques, the other

approaches are briefly discussed. They should not be ignored when attempting to

control exposure to chemicals by ventilation.

The occupational health professional should always think of the concept of source-

path-receiver. The primary focus should be on control at the source with control of

the path the second focus. Control at the receiver should be considered the last

choice. Whether it is during the start-up or design phases of a process or during the

evaluation of an existing process, the procedure for control of exposure to air

contaminants should start at the source and progress to the receiver. It is likely that

all or most of these control strategies will need to be used.

Substitution

The principle of substitution is to eliminate or reduce the hazard by substituting non-

toxic or less toxic materials or redesigning the process to eliminate escape of

contaminants into the workplace. Ideally, substitute chemicals would be non-toxic or

the process redesign would completely eliminate exposure. However, since this is

not always possible the subsequent controls in the above hierarchy of controls are

attempted.

Note that extreme care should be taken to assure that substitution does not result in

a more hazardous condition. While this focus is on the toxicity hazard, the flammable

and chemical reactivity of substitutes must also be considered when assessing this

risk.

Isolation

The principle of isolation is to eliminate or reduce the hazard by separating the

process emitting the contaminant from the worker. This is accomplished by

completely enclosing the process or locating it a safe distance away from people.

However, to accomplish this, the process may need to be operated and/or controlled

remotely. Isolation is particularly useful for jobs requiring few workers and when

control by other methods is difficult. Another approach is to perform hazardous

operations on off shifts where fewer workers may be exposed. Sometimes the use of

this technique does not eliminate exposure but reduces the number of people who

are exposed.

Ventilation

Two types of exhaust ventilation are commonly employed to minimize airborne

exposure levels of contaminants. The first is called general or dilution ventilation.

The second is referred to as source control or local exhaust ventilation (LEV) and is

discussed in more detail later in this article.

These two types of exhaust ventilation should not be confused with comfort

ventilation, whose main purpose is to provide measured amounts of outdoor air for

breathing and to maintain design temperature and humidity.

Work Practices

Work practices control encompasses the methods workers employ to perform

operations and the extent to which they follow the correct procedures. General

concepts such as education and training, principles of management and social

support systems include discussions of the importance of work practices in

controlling exposures.

Personal Protective Equipment

Personal protective equipment (PPE) is considered the last line of defense for control

of worker exposure. It encompasses the use of respiratory protection and protective

clothing. It is frequently used in conjunction with other control practices, particularly

to minimize the effects of unexpected releases or accidents. These issues are

discussed in more detail in the chapter Personal protection.

Local Exhaust Ventilation

The most efficient and cost-effective form of contaminant control is LEV. This

involves capture of the chemical contaminant at its source of generation. There are

three types of LEV systems:

1. enclosures

2. exterior hoods

3. receiving hoods.

Enclosures are the preferable type of hood. Enclosures primarily are designed to

contain the materials generated within the enclosure. The more complete the

enclosure the more completely the contaminant will be contained.

Because safety data sheets often do not adequately consider the special use of a

product, specialists in branches of industry compile information on product groups

(e.g., cooling lubricants for practical work protection in the factory) from producers’

information and substance data. Product groups are defined according to their use

and their chemical risk potential. The information made available on product groups

is independent of the data provided by producers on the composition of individual

products because it is based on general formulae of composition. Thus, the user has

access to a supplementary independent information source in addition to the safety

data sheet.