How to do a COSHH assessment
Reviewed September 2026 · Written by Complys and checked against HSE and legislation.gov.uk guidance (sources below).
A COSHH assessment isn't about filing safety data sheets — it's about working out how a substance could harm the people doing a specific task, and what will actually control that. Here's a practical, HSE-aligned method.
1. Gather the substance information
Start with the supplier's safety data sheet for each product, plus any workplace exposure limit from HSE's EH40. The safety data sheet tells you the intrinsic hazards — it is an input to your assessment, not the assessment itself.
2. Work out who is exposed, and how
Identify everyone who could be exposed — not just the operator, but people nearby, cleaners and maintenance staff — and by which route: breathing it in, absorption through the skin, or ingestion. Different routes need different controls.
3. Evaluate the risk
Judge how much is used, how often, for how long, and in what conditions (enclosed space, poor ventilation, heat). A tiny amount used once is a very different risk from the same substance used all day in a confined area.
4. Decide the controls — in the right order
Work down the hierarchy: eliminate the substance, or substitute a safer one; then engineering controls such as enclosure or local exhaust ventilation; then ways of working that reduce exposure; and only then PPE and RPE, to supplement the rest. Check any workplace exposure limit won't be exceeded.
5. Record it and tell people
Record the significant findings (required if you employ five or more), and make sure the people doing the work know the hazards, the controls and what to do in an emergency or spill. A control nobody knows about controls nothing.
6. Review it
Review regularly, and straight away if the substance, process or quantities change, or if monitoring shows the controls aren't working. A COSHH assessment is a living document, not a one-off.
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Sources
- HSE — COSHH assessments
- COSHH 2002, reg 6 (assessment of health risks)
- HSE — Control the risks (COSHH)
- HSE — EH40/2005 Workplace exposure limits
This guide is general information, not legal advice. COSHH and chemical-classification rules change over time — always check the current HSE and legislation.gov.uk guidance for your work.
How to do a COSHH assessment — FAQs
What are the steps of a COSHH assessment?
Gather substance information (safety data sheets, exposure limits), identify who is exposed and how, evaluate the risk (amount, frequency, conditions), choose controls using the hierarchy, record the findings and train people, then review.
Is a safety data sheet a COSHH assessment?
No. A safety data sheet describes a product's intrinsic hazards and is an input to your assessment. The COSHH assessment evaluates your specific task, quantities, exposure and controls.
What is the hierarchy of control for COSHH?
Eliminate or substitute the substance first; then engineering controls such as local exhaust ventilation; then ways of working; and PPE/RPE last, only to supplement the other controls.