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Workplace Exposure Limits (EH40)

Introduction to EH40

Many people are exposed to a variety of substances at work, eg chemicals, fumes, dusts etc, which can have a harmful effect on their health. If exposure to these hazardous substances is not properly controlled, it may cause ill health in a number of ways.

This table contains the HSEs EH40 guidance about:​

  • workplace exposure limits

  • approved workplace exposure limits

European occupational exposure limits

Indicative Occupational Exposure Limit Values (IOELVs) are health-based limits set under the Chemical Agents Directive (98/24/EC).


The Scientific Committee on Occupational Exposure Limits (SCOEL) advise the European Commission on limits. This committee evaluates the scientific information available on hazardous substances and makes recommendations for the establishment of an IOELV. IOELVs are listed in Directives which Member States are obliged to implement by introducing national limits for the substances listed.

IOELV Directives require Member States to establish national occupational exposure limits for the chemical agents in question, taking into account the European values. In most cases, this will mean that the British limit will be identical, or very close to the IOELV.

Workplace exposure limits (WELs)

WELs are British occupational exposure limits and are set in order to help protect the health of workers. WELs are concentrations of hazardous substances in the air, averaged over a specified period of time, referred to as a time-weighted average (TWA). Two time periods are used:

  • long-term (8 hours); and

  • short-term (15 minutes).

Short-term exposure limits (STELs) are set to help prevent effects such as eye irritation, which may occur following exposure for a few minutes.


The information on this site is updated and checked for accuracy and completeness from time to time. However it is important to note that legal information must be used with a degree of caution.

Users must be aware that whilst an Act, Statutory Instrument (SI), Regulation or Guidance may still be in force, parts may have been superseded or completely withdrawn.

Any withdrawn or amended sections will still be contained within the Act, SI, Regulation and Guidance and there will be nothing in the document to identify those sections that no longer apply.

Please seek independent legal advice.

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