COSHH Risk Assessment Step 3: Prevent or adequately control exposure

Workplace exposure limits

You must ensure that exposure to a hazardous airborne substance doesn't exceed the workplace exposure limit (WEL). If the substance causes cancer, inheritable genetic damage or asthma, you must reduce exposure to the lowest level as reasonably possible.

You can check the levels of WELs for a number of hazardous substances on the HSE website.

Correctly applying the principles of good practice will mean exposure is controlled below the WEL. Advice on applying the principles can be found in the COSHH Approved Code of Practice (PDF).

Controlling of particular hazards

You must keep exposure to substances that cause cancer, inheritable genetic damage or asthma to the minimum possible level.

Special requirements apply to carcinogens (substances that may cause cancer), or mutagens (substances which may cause heritable genetic damage). See Appendix 1 of the COSHH Approved Code of Practice.

If there is no WEL or if exposure can be by absorbing it through the skin or by swallowing it, you must set a minimum standard so that no one will fall ill. Before setting a standard, consider all appropriate information, e.g. safety data sheets, the Health and Safety Executives' (HSE, or HSENI in Northern Ireland) guidance, technical papers and occupational medicine/hygiene journals.