The Control of Substances Hazardous to Health (COSHH) regulations play a key part in health and safety procedures for most businesses. As an employer it is essential that the COSHH regulations are adhered to and understood so the workforce can be kept safe from harm; failure to do could lead to criminal prosecution.

COSHH sets out a hierarchy of control measures to protect people’s health arising from immediate or delayed exposure to hazardous substances used in or generated from workplace practices.

These substances can include:

  • biological agents (fungi, bacteria, viruses);
  • natural substances (grain, flour, enzyme dusts, etc.);
  • substances generated by work (e.g. welding fumes or wood dust);
  • chemical products used or produced at work (e.g. adhesives or cleaning agents).

This topic page focuses on the risk of illness and disease as a consequence of contact with hazardous substances via skin, inhalation or ingestion. For guidance on fire and explosion hazards refer to:

Process-related fire and explosion hazards

Storage and use of flammables and explosives

To protect your employees from the exposure to hazardous substances you need to do the following:
  • Identify what hazards there are within the workplace and activities
  • Decide on how to prevent them by a competent person undertaking a risk assessment
  • Implement any necessary control measures to reduce exposure and ensure they are properly utilised which will involve informing, instructing and training employees about the risks and any necessary precautions that they need to take to work safely
  • Regularly review the assessment and maintain control measures and ensure that any statutory inspections are completed for example, local exhaust ventilation (LEV)
  • Provide monitoring and health surveillance (if required)
  • Plan for emergencies such as fire, leaks or spillages or the sudden release or the failure of LEV


Around 500 hazardous substances have been assigned Workplace Exposure Limits (WELs) by HSE. WELs are intended to prevent excessive exposure to the substances by containing the exposure to below the specified limit.  These are primarily set for airborne substances and can be either a short term limit or long term over an 8 hour day.  The HSE publication EH40/2005 sets out these limits and is reviewed annually.

As part of the assessment process you should involve your employees as they may notice things that are not obvious and may have some ideas on how to control the risks. 

Once all possible situations have been identified you need to determine how harm can be prevented by either removing or reducing the risk. If you’re unable to remove the risk, the implementation of control measure is a must. Control measures should be approached in the following order:
using the substance where possible.

the process so the substance can't escape, and/or extract emissions from the substance near the source, through exhaust ventilation.
the substance with a safer alternative be that by using a less harmful substance or different form of the substance or change the process to reduce or limit the amount of needed.
the number of employees who could be exposed to the hazard even with control measures in place.

as a last resort provide personal protective equipment (PPE) to staff who are exposed to the hazardous substance.
Any control measures implemented should follow the eight principles of good practice set out in Schedule 2A of the COSHH regulations. These principles must all be applied to obtain effective and reliable control, and overlap in their application. These are the eight principles of good practice:
1. Design and operate processes and activities to minimise emission, release and the spread of substances hazardous to health.

2. Take into account all relevant routes of exposure (inhilation, skin absorption and ingestions) when developing control measures.

3. Control exposure by measures that are proportionate to the health risk.

4. Choose the most effective and reliable control options which minimise the escape and spread of substances hazardous to health.
5. Where adequate control of exposure cannot be achieved by other means, provide, in combination with other control measures, suitable protective equipment for employees.
6. Regularly check and review all elements of control measures to ensure continuing effectiveness.
7. Inform and train all employees on the hazards and risks of the substances they work with and ensure they use the control measures developed to minimise the risks.
8. Ensure that the introduction of control measures does not increase the overall risk to health and safety.


Health Surveillance is necessary where have substances with known health effects or disease and there is a reasonable likelihood of the effect or disease occurring.

Additionally undertaking these checks will help to detect as early as possible any adverse changes and ensure that can prevent a more serious disease from developing and ensures that control measures are working effectively.

Health surveillance may necessitate medical surveillance by occupational health provider or can be undertaken by an appropriately trained employee, depending upon the nature of the substance. 

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