A COSHH assessment is the process an employer uses to identify hazardous substances in the workplace, work out who could be exposed and how, and decide what controls are needed to keep that exposure safe. It’s required under the Control of Substances Hazardous to Health Regulations 2002, and it applies to almost any UK workplace that uses, stores, or generates a substance capable of causing harm.
A COSHH assessment systematically identifies the hazardous substances present in a workplace, evaluates the health risks they pose, and sets out the control measures needed to reduce or eliminate exposure.
In practice, it needs to answer:
These questions apply whether the substance is bought in or produced as a by-product of the work itself, such as dust or fume.
| Substance category | Examples |
| Chemicals and chemical products | Cleaning agents, adhesives, solvents |
| Dusts | Wood dust, flour, silica |
| Fumes | Welding fume, soldering fume |
| Vapours and gases | Solvent vapour, chlorine |
| Biological agents | Bacteria, viruses, fungi |
| Nanomaterials and process-generated substances | Substances created by the work itself, not just those bought in as products |
Asbestos, lead, and radioactive substances are controlled under their own separate regulations, though COSHH principles often still apply alongside them.
COSHH assessments apply to a wide range of substances, including:
Chemicals and products containing chemicals (e.g., cleaning agents, adhesives)
Fumes from welding or soldering
Dusts such as wood, flour, or silica
Vapours and gases including solvents or chlorine
Biological agents like bacteria, viruses, or fungi
Nanomaterials and substances generated during work activities
Note: Asbestos, lead, and radioactive substances follow separate regulations, although COSHH principles may still apply. Therefore, understanding the differences is important.
Using a generic template instead of a workplace-specific assessment
Over-relying on PPE rather than working through the fuller hierarchy of controls
Overlooking substances generated by the work itself, such as dust or fume, rather than only those bought in
Poor communication of the risks and controls to the people actually exposed to them
Treating the assessment as a one-off, with no follow-up monitoring or review
The terms COSHH assessment and chemical risk assessment are often used interchangeably, and in practice they usually describe the same exercise: assessing the risk posed by a hazardous substance. COSHH is the specific legal mechanism, set out under COSHH Regulation 6, that requires it.
A general risk assessment is broader and covers hazards such as slips, trips, machinery, and manual handling. COSHH assessments are narrower but deeper: they require an understanding of chemical properties, health effects, and control strategies that a general risk assessment doesn’t need to cover. Depending on complexity, that expertise may need to come from an occupational hygienist or other qualified health professional rather than being handled entirely in-house.
For straightforward, low-risk situations, such as a small quantity of a well-understood cleaning product, a competent person within the business can often complete the assessment using the product’s safety data sheet and HSE’s COSHH Essentials tool.
More complex exposure, multiple substances, higher-risk processes such as welding or cutting, or genuine uncertainty about whether existing controls are adequate, is where a qualified occupational hygienist earns their place. We’re BOHS-accredited COSHH specialists, and our standard report turnaround is 15 working days. Where a COSHH assessment points to a wider compliance gap, our COSHH compliance service covers the regulations in full, from risk assessment through to training.
It depends on the number of substances and processes involved. A single-substance, low-risk assessment might take a few hours; a multi-site assessment covering several processes takes longer and is usually scoped in advance.
There’s no single mandatory qualification for straightforward assessments, but the person doing it needs to genuinely understand the substances and controls involved. For higher-risk situations, a BOHS-accredited occupational hygienist is the standard route.
Yes. COSHH applies regardless of frequency. Occasional use may reduce the risk level and the scope of controls needed, but it doesn’t remove the legal requirement to assess it.
Nothing meaningful. Both describe the same process. “COSHH risk assessment” is simply the more literal phrasing of the same requirement.
For more on employer and employee responsibilities under COSHH, see our full COSHH FAQs.
