COSHH stands for the Control of Substances Hazardous to Health Regulations 2002. It's the UK law that requires employers to assess and control the risks from hazardous substances in the workplace — chemicals, dusts, fumes, gases, and biological agents. Employers must identify hazardous substances, carry out a COSHH assessment, implement controls following the hierarchy of risk control, provide information and training to workers, and monitor exposure where necessary. COSHH applies to almost every UK workplace, from offices using cleaning products to manufacturing plants handling industrial chemicals.
If your workplace uses any chemicals, generates dust or fumes, or exposes workers to biological agents, COSHH applies. This guide explains what the regulations require, how to comply, and where the most common failures happen.
COSHH stands for Control of Substances Hazardous to Health. The current regulations are the Control of Substances Hazardous to Health Regulations 2002 (often abbreviated as COSHH 2002 or CoSHH), which replaced earlier versions dating back to 1988.
The regulations are made under the Health and Safety at Work etc. Act 1974 and are enforced in the UK by the Health and Safety Executive (HSE) and local authorities depending on the workplace.
COSHH covers any substance that is hazardous to health, including:
Some hazardous substances have their own dedicated regulations and fall outside COSHH:
COSHH applies to virtually every UK workplace. The duty falls primarily on the employer, but workers and contractors also have duties:
There's no minimum employer size — even sole traders using cleaning chemicals at a client's premises have COSHH duties.
| Duty | What it requires |
|---|---|
| 1. Assess the risks | Identify hazardous substances used or generated, who's exposed, how, and at what level. This is the COSHH assessment. |
| 2. Decide what precautions are needed | Apply the hierarchy of control. Eliminate, substitute, engineer, administrate, then PPE — in that order. |
| 3. Prevent or adequately control exposure | Implement the controls identified. Adequate control means below relevant Workplace Exposure Limits (WELs) where they apply. |
| 4. Ensure controls are used and maintained | Engineering controls (extraction, ventilation) require regular thorough examination and testing — typically every 14 months. |
| 5. Monitor exposure | Where adequate control can't be confirmed without measurement, exposure must be monitored — typically by an occupational hygienist. |
| 6. Health surveillance | For specific exposures (e.g. respiratory sensitisers, skin sensitisers), health surveillance is required by occupational health professionals. |
| 7. Provide information, instruction and training | Workers must understand what they're handling, the risks, the controls, and what to do in emergencies. |
| 8. Plan for emergencies | Spills, leaks, accidents — procedures, equipment and training for foreseeable emergencies. Practical spill response is most often where this duty is weakest in audit; our Spill Kits and Chemical Control course covers the operational training that supports this duty. |
The COSHH assessment is the cornerstone of compliance. The 7-step approach:
Producing a robust COSHH assessment is a discipline in itself, separate from the general principles of risk assessment. The person doing the work needs to be able to read a safety data sheet competently, understand exposure pathways, evaluate whether existing controls are actually adequate against the substance's properties, and document the outcome in a way that survives audit and feeds into worker training. Our COSHH Assessors Training course covers this in-house competence specifically. Most employers running structured COSHH compliance settle on a model where one or two trained assessors handle the assessment work, supported by wider COSHH Awareness training across the workforce who actually handle the substances.
COSHH explicitly requires controls to follow the hierarchy of risk control:
The HSE has been clear that PPE-only solutions rarely demonstrate adequate control. A COSHH assessment that identifies a hazard and concludes "we'll issue gloves and masks" is usually inadequate — engineering controls should normally be considered first.
For many hazardous substances, the HSE publishes Workplace Exposure Limits (WELs) in document EH40. WELs set a maximum legal concentration in workplace air — exposure above the WEL is unlawful regardless of how the substance is being controlled.
WELs come in two types:
Where a WEL exists, achieving exposure below it is a minimum legal requirement. Not all substances have WELs — for those, "adequate control" is determined by professional judgement.
The most common failure. Either no assessment exists, or the assessment is a generic template that doesn't reflect actual workplace use.
Safety data sheets describe the substance generically. A COSHH assessment must apply that information to your specific workplace — how the substance is actually used, by whom, in what volumes.
Issuing gloves and masks without considering whether engineering controls (extraction, enclosure) would prevent exposure in the first place. Inspectors will challenge this.
Local exhaust ventilation requires thorough examination and testing every 14 months. A faded sticker on the side of an extraction unit is a common audit finding.
Workers using hazardous substances without information about what they're handling. The "right to know" is fundamental to COSHH compliance.
COSHH stands for Control of Substances Hazardous to Health Regulations 2002. It's the UK law governing workplace exposure to hazardous substances.
Almost all. Any workplace using hazardous chemicals (including cleaning products), generating dusts, fumes, or biological agents falls under COSHH. There's no minimum employer size.
At least annually, and additionally when substances or processes change, when exposure may have increased, after incidents, or when health surveillance reveals problems.
Any competent person with sufficient knowledge of the substances, the workplace, and risk assessment principles. For complex substances or exposures, occupational hygiene specialists may be needed.
Yes. COSHH explicitly requires employers to provide information, instruction and training to workers exposed to hazardous substances.
A safety data sheet (SDS) describes the substance generically — its hazards, properties, and recommended controls. A COSHH assessment applies that information to your specific workplace use — how it's actually handled, by whom, in what volumes, with what existing controls.
Anyone responsible for handling, supervising or assessing hazardous substances should have appropriate training. KeyOstas offers options at every level:
For consultancy support on COSHH assessments, see our Risk Assessment & Management consultancy. Or call us on +44 (0) 3300 569534.
