COSHH explained in plain English

COSHH explained in plain English – Tutwoo study guide

COSHH stands for the Control of Substances Hazardous to Health Regulations 2002. It’s the law in Great Britain that requires employers to control substances that can harm people’s health at work. This guide explains what it covers and what it asks of employers and workers.

What counts as a hazardous substance

COSHH covers a wide range of things, including:

  • chemicals, and products that contain them
  • fumes, dusts, vapours, mists and gases
  • nanotechnology
  • biological agents, such as germs

HSE says a product with a hazard symbol on its packaging is classed as a hazardous substance. Some substances have their own separate rules instead, including lead, asbestos and radioactive substances.

What employers must do

HSE sets out the main steps:

  1. Find out what substances are used or produced, and what harm they can do.
  2. Assess the risk to workers and anyone else who could be affected.
  3. Prevent or control exposure.
  4. Make sure controls are used and maintained.
  5. Give information, instruction and training to workers.
  6. Monitor exposure and provide health checks where needed.
  7. Plan for emergencies.

The order of control

The law says employers should prevent exposure first. Swapping a hazardous substance for a safer one is the preferred way to do this. Where exposure can’t be prevented, it must be adequately controlled, in this order:

  1. Change the work process, or use engineering controls and equipment.
  2. Control the substance at its source, for example with extraction or ventilation, and organise the work to reduce exposure.
  3. Use personal protective equipment (PPE) such as gloves or masks, only as a last resort and on top of the other measures.

Safety data sheets and hazard symbols

Suppliers must give you an up-to-date safety data sheet for a dangerous substance. It explains the hazards and how to handle the product safely, so use it in your risk assessment.

Hazardous products carry hazard pictograms: diamonds with a red border and a white background. There are nine, covering hazards such as flammable, corrosive, acute toxicity, serious health hazard, and hazardous to the environment.

Workplace exposure limits

About 500 substances have a workplace exposure limit (WEL): a legal limit on how much of the substance can be in the air people breathe, averaged over a set time. HSE publishes the list in a document called EH40/2005. Where a WEL exists, exposure must not exceed it. For substances that can cause cancer, genetic damage or asthma, exposure must also be kept as low as reasonably practicable.

What workers must do

Workers must make full and proper use of the controls provided, return equipment such as PPE to its storage after use, and report any defects straight away.

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Sources

This guide is general information, not legal advice. Tutwoo is independent and not affiliated with HSE. Details from hse.gov.uk and legislation.gov.uk, checked 31 October 2026.

© 2026 Tutwoo UK Limited. This guide was created in-house by Tutwoo and is our original work. It is for your own learning only: please do not copy, share, record or resell it.