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6. Operational control measures

6.1 General principles

6.1.1. The competent authority should ensure that criteria are established for safety in the use of hazardous chemicals including criteria for the measures outlined in sections 6.4 (Elimination) to 6.9 (measures for disposal and treatment).

6.1.2. After reviewing the chemicals being used at work, obtaining information about their hazards and making an assessment of the potential risks involved, employers should take steps to limit exposure of workers to hazardous chemicals, on the basis of the measures outlined in sections 6.4 to 6.9, in order to protect workers against hazards from the use of chemicals at work. The measures taken should eliminate or minimise the risks, preferably by substitution using non-hazardous or less hazardous chemicals, or by the choice of technology; but where this cannot be achieved the risks should be eliminated or minimised using good engineering controls. Other measures such as safe working systems and practices, personal protective equipment and the provision of information and training will further minimise risks and may have to be relied upon for some activities entailing the use of chemicals.

6.1.3. For new work activities involving the use of chemicals, the hazards should be identified and the risks assessed at the earliest stage when the new work activity is being considered. The hazards and risks should be reviewed at each subsequent stage in the development of a new process.

6.1.4. The purpose of the assessment is to enable an informed decision to be made by employers about the validity of measures to eliminate or minimise risks from chemicals. Employers should show that all aspects of the use of chemicals have been considered in the assessment. Where an employer identifies risks which can or should be eliminated or minimised he or she should eliminate or minimise these risks as soon as possible and by the best possible means following the order of preference in the measures outlined in paragraph 6.1.2. A programme should be prepared to specify the action necessary to eliminate or minimise the risks and the time for completion.

6.1.5. For complex work activities, such as the manufacture of chemicals, the hazards of the process may be identified by breaking down the process into its component operations; the stages for reviewing risks may include a desk study (a paper review of the process and known risks), laboratory development work, pilot plant operations, commissioning and full operation of plant.

6.1.6. Hazardous chemicals might be used in quantities which have the potential to be a major risk not only to workers, but also to the population in the vicinity of the use of the chemicals and to the general environment. The use of such chemicals should additionally be controlled by following the objectives and procedures of the ILO code of practice, Prevention of major industrial accidents (Geneva, 1991), and in accordance with national law and practice.

6.2 Procedures for assessment

6.2.1. The assessment should be carried out by employers or by persons acting on their behalf who have the necessary Information, instruction and training and are competent to do so. It should include:

(a) Assessment of risks

This should include consideration of which chemicals are used and the nature of their hazards, i.e. whether they may present a risk of one or more of the following:

1. acute or chronic ill health by entry into the body through inhalation, skin absorption or ingestion;
2. injury or ill health from skin or eye contact;
3. injury from fire, explosion or other events resulting from physical properties or chemical reactivity;

(b) Appraisal of control measures

An estimate of risk, and whether it can be eliminated, should be made, taking into account the engineering control measures and systems of work. The estimate should cover the hazards and control measures outlined in sections 6.5 (control measures) to 6.9 (measures for disposal and treatment). In estimating health risks, account should be taken of exposure limits or other exposure criteria specified, approved or recognised by the competent authority. Personal protective equipment should only be taken into account as a method of control where other measures have been taken but are not sufficient;

(c) Action programme

The estimated risk should be compared with criteria that have been formulated, agreed or recognised by the competent authority for safety in the use of chemicals and a programme of work drawn up based on these established criteria or, where such criteria do not exist, other valid criteria.

6.2.2. The assessment of risks should take into account:

(a) the quantity of the chemical present at the workplace;

(b) the operating conditions and processes applied at the workplace;

(c) the range of uses of chemicals for which the employer is responsible, which might include production, handling, storage, transport and disposal;

(d) the variety of tasks that contribute to a work activity, particularly those where the engineering controls provided are not available, e.g. during certain maintenance, breakdown or cleaning tasks;

(e) the nature of the chemical and whether the hazards and associated risks are increased by the way it is used, e.g. at high temperatures and pressures;

(f) the consequences and likelihood of a possible failure or sequence of failures of the control measures provided.

6.2.3. Atmospheric sampling should be used where appropriate. It may be used as a control parameter for the effectiveness of measures provided, and in particular for assessing exposure where operations or tasks are complex and the chemicals involved have established exposure limits.

6.3 Review of assessment

6.3.1 The assessment should be reviewed whenever there is reason to suspect that it is no longer valid or where there has been a significant change in the work to which the assessment relates.

6.3.2 The assessment may be shown to be no longer valid because of, for example:

(a) the results of periodic thorough examinations and tests of engineering controls;

(b) an incident which led or was liable to lead to a fire or explosion;

(c) the results of monitoring exposure at the workplace, the results of health or medical surveillance, or a confirmed case of occupationally induced disease;

(d) new information on health hazards, or on fire and explosion risks.

6.3.3 A significant change in the work may consist of:

(a) a change in the substances used or their source;

(b) plant modification, including engineering controls;

(c) a change in the process or methods of work;

(d) a change in the volume or rate of production.

6.4 Elimination

6.4.1. Employers should include in their assessment consideration as to whether the risks from the hazardous chemicals used can be eliminated by:

(a) ceasing to use the chemicals;

(b) replacing them by less hazardous chemicals or by the same substances in a less hazardous form. Care should be taken to consider all the known risks of the proposed substitutes, and action should be taken on precautionary measures before substitution;

(c) using an alternative process.

6.4.2. Where the use of hazardous chemicals cannot be prevented, the control measures outlined in sections 6.5 (health related measures), 6.6 (measures related to properties), 6.7 (measures for storage), 6.8 (measures for transport) and 6.9 (measures for disposal and treatment) should be followed.

6.5 Control measures for chemicals hazardous to health

6.5.1. Workers should be protected against the risk of injury or disease from chemicals hazardous to health. Workers should not be exposed to chemicals hazardous to health, in particular to an extent 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 recognised by the competent authority in accordance with national or international standards.

6.5.2. Control measures to provide protection for workers could be any combination of the following:

(a) good design and installation practice:

1. totally enclosed process and handling systems;
2. segregation of the hazardous process from the operators or from other processes;
3. plants processes or work systems which minimise generation of, or suppress or contain, hazardous dust, fumes, etc., and which limit the area of contamination in the event of spills and leaks;
4. partial enclosure, with local exhaust ventilation;
5. local exhaust ventilation;
6. sufficient general ventilation;

(b) work systems and practices:

1. reduction of the numbers of workers exposed and exclusion of non-essential access;
2. reduction in the period of exposure of workers;
3. regular cleaning of contaminated walls, surfaces, etc.:
4. use and proper maintenance of engineering control measures;
5. provision of means for safe storage and disposal of chemicals hazardous to health;

(c) personal protection:

1. where the above measures do not suffice, suitable personal protective equipment should be provided until such time as the risk is eliminated or minimised to a level that would not pose a threat to health;
2. prohibition of eating, chewing, drinking and smoking in contaminated areas;
3. provision of adequate facilities for washing, changing and storage of clothing, including arrangements for laundering contaminated clothing;
4. use of signs and notices;
5. adequate arrangements in the event of an emergency.

6.6 Control measures for flammable, dangerously reactive or explosive chemicals

6.6.1. Workers should be protected against risks of injury resulting from the use of flammable, unstable or explosive chemicals. A combination of the following measures should be used to reduce the risk of a fire or explosion.

(a) Good design and installation practice:

In addition to the fundamental principles in paragraph 6.5.2 (a) (good design) which should be applied to eliminating flammable vapours, fumes or dusts liable to be given off, the following practices should also be observed where appropriate:

1. elimination or control of sources of ignition;
2. separation of processes that use flammable chemicals from:
   • other processes;
   • bulk storage of the flammable chemicals or bulk storage which may cause a hazard in the event of fire;
   • the boundary and premises off site, which are not under the control of the employer; and
   • fixed sources of ignition;
3. provision of an inert atmosphere for totally enclosed processes and handling systems;
4. provision of means of fire detection and alarm which as far as is practicable, should include automatic means of extinguishing incipient fires;
5. installation of means for detecting increases in pressure and the automatic operation of a gas suppressor to prevent an explosion, e.g. for dust explosions;

(b) Safe work systems and practices:

1. use and proper maintenance of the engineering control measures provided;
2. minimisation of the quantities of chemicals kept in the workplace;
3. minimisation of the quantities of chemicals handled and used in buildings;
4. separation of arrangements for storing chemicals from normal process activities;
5. separation of incompatible chemicals;
6. reduction of the numbers of workers exposed and exclusion of non-essential access;
7. arrangements for spillages to be cleared up immediately;
8. arrangements for the safe disposal of chemicals;
9. ensuring that appropriate equipment is provided, e.g. non-sparking tools for low-incentive materials in specified situations;
10. use of appropriate signs and notices;

(c) Personal protection:

1. ensuring that where personal protective equipment and general work clothing are provided, they are not liable to increase the possibility of serious burns. Certain synthetic materials may melt in a fire and thereby cause more serious burns;
2. making adequate preparations for an emergency.

6.6.2. The adequacy of the means of escape, fire-fighting arrangements, the fire alarm system and provisions for the evacuation of the premises should be considered, following the assessment of chemicals that may be flammable, unstable or explosive.

6.7 Control measures for the storage of hazardous chemicals

6.7.1. Hazardous chemicals should be stored under conditions specific to their inherent properties and characteristics to ensure safety and in accordance with established criteria. Chemicals with typical properties and characteristics that are relevant include:

(a) flammable liquids;
(b) flammable gases;
(c) toxic chemicals;
(d) corrosive chemicals;
(e) chemicals that emit highly toxic fumes in the event of a fire;
(f) chemicals which, in contact with water, give off flammable gas;
(g) oxidising chemicals;
(h) explosives;
(i) unstable chemicals;
(j) flammable solids;
(k) compressed gases.

6.7.2. Chemicals known to have carcinogenic, mutagenic or teratogenic health effects should be kept under strict control.

6.7.3. Many standards, codes or guidelines exist concerning the storage of specific chemicals in bulk or in small containers. Where smaller containers (e.g. drums, cylinders, sacks or bags) are used, intermixing of chemicals is liable to occur. The major risk is that of fire and the resultant release of chemicals or combustion products. Many incidents of loss or injury resulting from warehouse activities have been caused by fire. With these fundamental points in mind, the control measures to provide protection should cover any combination of the following:

(a) the compatibility and segregation of stored chemicals. Chemicals that can react together to form unstable or noxious products, or produce heat, should be kept separate. Because of their reactivity and their liability to produce heat, oxidising chemicals should be kept separate from flammable liquids or other flammable chemicals;

(b) limitations on quantities of chemicals to be stored. This applies to chemicals with certain characteristic properties, so as to limit the effects of an accident or incident involving (or liable to involve) the chemicals in an emergency;

(c) adequate security of and access to storage areas. Potential ignition sources should be prohibited or controlled;

(d) safe sitting of storage areas. In order to minimise the effects of an incident, storage areas for chemicals should be kept separate from process areas, occupied buildings and other storage areas, as well as from boundaries and off-site premises over which the employer has no control, and fixed sources of ignition, except for a small quantity of a hazardous chemical stored in a workplace in a safe manner (e.g. a small amount of a flammable liquid in a fire-resistant cabinet);

(e) the appropriate construction, nature and integrity of storage containers:

(f) safe loading and unloading of storage containers. Criteria relating to suitable equipment and safe systems of Work including training, are of primary importance for (f), (g) and (h);

(g) adequate precautions against accidental release, fire, explosion and chemical reactivity;

(h) adequate precautions and procedures in case of spillage;

(i) temperature, humidity and ventilation requirements. These are particularly important where the ambient temperature and humidity are high. Ventilation requirements should ensure that there is no accumulation of gases, vapours or fumes in enclosed areas;

(j) labelling and relabelling requirements;

(k) emergency procedures;

(l) requirements relating to possible physical and chemical changes in stored chemicals (e.g. not to store beyond the expiration period recommended on the label and the chemical safety data sheet);

(m) deployment of surveillance systems.

6.8 Control measures for the transport of chemicals

6.8.1. Hazardous chemicals should be transported in accordance with criteria established by the competent authority for the safety of the workers involved.

6.8.2. The criteria established by the competent authority should be consistent with national or international transport regulations and cover, as applicable:

(a) the properties and quantity of chemicals to be transported;

(b) the nature, integrity and protection of the packaging and containers used in transport, including pipelines;

(c) the specifications of the vehicle used in transport;

(d) the routes to be taken;

(e) the training and qualifications of transport workers;

(f) labelling requirements;

(g) loading and unloading;

(h) procedures in case of emergency, e.g. fire or spillage.

6.8.3. The criteria that are established should be consistent with the criteria of existing international transport requirements (e.g. the International Maritime Dangerous Goods Code, the Convention on International Civil Aviation and, in Europe, the European Agreement concerning the International Carriage of Dangerous Goods by Road (ADR)), which cover goods moving between countries and which are primarily aimed at protecting the environment and persons (other than the transport workers concerned) who may be involved in transport accidents.

6.8.4. The criteria should complement the above by:

(a) providing protection for workers; and

(b) providing protection for other persons who may be involved in a transport accident involving hazardous chemicals being transported internally within a country or within a workplace.

6.9 Control measures for the disposal and treatment of chemicals

6.9.1. The disposal of chemicals no longer required and the risks to workers should be included in the employers' assessment of risks. The chemicals should also be handled, treated or disposed of in a manner which eliminates or minimises the risk to safety and health and to the environment, in accordance with national law and practice. Containers which have been emptied but which may contain residues of hazardous chemicals should be treated as hazardous.

6.9.2. Hazardous chemicals deemed to be waste should be disposed of according to procedures based on criteria established by the competent authority or laid down in standards, codes or guidelines which have been approved or recognised by the competent authority for the treatment and disposal of hazardous chemicals and hazardous waste products, with a view to ensuring the safety of workers; these criteria should be consistent with the protection of the general public and the environment.

6.9.3. The criteria established by the competent authority should be consistent with national or international regulations regarding disposal and treatment of hazardous waste and should cover, where applicable:

(a) the method of identification of waste products. Waste products should be identified as waste, by their origins and also by their main components, where known. The main components should be determined from the history of the products. In cases of doubt about the degree of hazard, the waste should be classified as the highest hazard;

(b) the handling of contaminated containers. Empty containers which have not been cleansed of hazardous chemicals should be closed and stored to await disposal or reuse, and treated as if they contained those hazardous chemicals. Empty containers should retain the identification, marking and labelling of their previous contents;

(c) the identification, construction, nature, integrity and protection of waste containers. The waste containers should be designed or chosen to provide protection to workers against the hazards identified in (a) and (b) above, taking into account the methods of work and disposal to be followed;

(d) the effects on the working environment. The discharge of effluent, the disposal and transport of waste, and the emission of smoke and chemicals into the atmosphere should be undertaken in such a way as to prevent or minimise risks to workers, or should be in accordance with national laws and practice for the protection of the general public and the environment;

(e) the demarcation of disposal areas. Disposal areas and storage areas for waste products should be set aside. Sufficient space should be provided on site to prevent the presence of waste containers in the normal process and storage areas;

(f) the provision, maintenance and use of personal protective equipment and clothing. Personal protection should be provided against the hazards referred to in (a) and (b) above and in accordance with the method of work to be followed;

(g) the method of disposal or treatment. Where there are no on-site facilities to dispose of waste safely, hazardous waste products should be disposed of through a specialist contractor in accordance with national laws and practice. Where an employer disposes of waste (e.g. waste flammable solvents and residues) by burning, this should be in a plant or process designed to do this safely and following a clearly defined system of work.

6.9.4. Guidelines concerning controls in respect of the transboundary movement of hazardous wastes can be found in the UNEP Basel Convention on the Control of Transboundary Movements of Hazardous Wastes and their Disposal.

6.10 Programme for action

6.10.1. Where the assessment of risks shows that the controls are inadequate or likely to become inadequate, risks should be eliminated or a programme should be prepared to minimise the risks and in any case to meet established criteria. Where these do not currently exist, valid criteria for the control of risks during the use of chemicals outlined in sections 6.5 (health-related measures), 6.6 (measures related to properties), 6.7 (measures for storage), 6.8 (measures for transport) and 6.9 (measures for disposal and treatment) should be drawn up by the employer. In preparing the programme, the general principles to be followed for the control measures in chapters 7 (Design and installation), 8 (Work systems and practices) and 9 (Personal protection) should be borne in mind, and attention paid to ensuring the adequacy of the information, instruction and training provided by employers, of the checking and monitoring systems and of the arrangements in the event of emergencies.

6.10.2. Each employer, after consultation with workers and workers' representatives, should establish and implement a programme to eliminate or minimise the identified risks in the use of hazardous chemicals. The programme should ensure that the risks are eliminated or minimised as soon as possible and by the best possible means. Preferred measures are by elimination or substitution of the hazardous chemicals involved, or where this cannot be achieved, by engineering controls. These measures may be difficult to complete immediately. Measures such as the provision of personal protective equipment may allow an earlier, though temporary, reduction in risks. The programme should specify the action necessary to eliminate or minimise the risks and the time for it to be completed.