COSHH Assessment UK: A Step-by-Step Guide for Employers (Regulations 2002)

The Control of Substances Hazardous to Health Regulations 2002 — COSHH — are the UK's main law protecting workers from hazardous substances. If your employees use chemicals, create dust or fumes, or work with biological agents, you need a written COSHH assessment before that work starts. It is not optional, and HSE inspectors are increasingly checking the *quality* of assessments, not just their existence.

The stakes are high. HSE's occupational lung disease statistics (published November 2025) estimate that around 11,000 people in Great Britain die each year from lung disease linked to past workplace exposures — dwarfing the roughly 124 acute work-related fatalities recorded each year. Much of that harm was preventable with a proper assessment and the controls that follow it.

This guide explains what COSHH requires, who must comply, how to carry out a suitable and sufficient assessment in eight steps, what the workplace exposure limits mean in practice, and what happens if you get it wrong.

What is COSHH and which substances does it cover?

COSHH stands for the Control of Substances Hazardous to Health Regulations 2002 (SI 2002/2677), made under the Health and Safety at Work etc. Act 1974. It applies across England, Scotland and Wales; Northern Ireland has an equivalent — the Control of Substances Hazardous to Health Regulations (Northern Ireland) 2003 — enforced by HSENI.

The regulations apply to any substance that can harm health, including:

• Chemicals and products containing chemicals — cleaning products, paints, adhesives, printing inks
• Fumes — welding fume, solder fume, fumes from hot-cutting
• Dusts — wood dust, flour dust, silica dust, grain dust, metal dust
• Vapours and mists — solvent vapours, spray paints, machining coolants
• Gases — carbon monoxide, chlorine, ammonia
• Biological agents — bacteria, viruses, fungi (for example in healthcare, waste handling or water systems)
• Substances created by the work itself — not just what you buy in a can

A common mistake is to think COSHH only covers things you purchase. Welding fume, silica dust from cutting stone, and dust created by sanding or polishing are produced *by the work* and are firmly inside COSHH. A separate category — substances that are hazardous only because they are flammable, explosive or at high temperature or pressure — sits outside COSHH and is controlled under the Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR).

Some hazards have their own specific legislation and are excluded from COSHH: asbestos (Control of Asbestos Regulations 2012), lead (Control of Lead at Work Regulations 2002) and radioactive substances (Ionising Radiations Regulations 2017). They still need managing — just under those regimes.

Who is responsible for a COSHH assessment?

Every employer and every self-employed person whose work could expose anyone to hazardous substances. That includes your own employees, contractors, visitors, customers and members of the public who could be affected.

Under Regulation 6 of COSHH, you must not carry out work that could expose anyone until you have made a suitable and sufficient assessment of the risks — one that identifies the hazards, who could be harmed, how, and what you will do about it. The depth of the assessment must be proportionate to the risk: a hairdresser's peroxide needs a lighter assessment than a spray booth.

There is no legal headcount threshold in COSHH itself. Under the Management of Health and Safety at Work Regulations 1999, employers with five or more employees must record their risk assessments, and HSE's COSHH Approved Code of Practice (L5) expects every COSHH assessment to be written down with specified content regardless of staff numbers. Recording the assessment is best practice at any size and is what inspectors will ask to see.

The 8-step COSHH assessment process

HSE's own guidance (HSG97, *A step-by-step guide to COSHH assessment*) breaks the process into steps. A compliant assessment covers:

1. Identify the hazardous substances. Walk every work activity and list every substance used, stored, produced or generated — including by-products like welding fume or sanding dust. Build a substance inventory. 2. Gather information on each substance. Suppliers must provide a safety data sheet (SDS) under UK REACH and CLP. Read sections 2 (hazards), 8 (exposure controls) and 11 (toxicological information), and check HSE guidance such as EH40 for the workplace exposure limit. 3. Decide who might be harmed and how. Consider the route of exposure — inhalation, skin contact, ingestion — plus who (employees, cleaners, contractors, neighbours), how often and for how long. 4. Evaluate the risk. Compare the actual level of exposure against the workplace exposure limit where one exists. Consider whether exposure is likely to be significant and what health effects could follow. 5. Decide on precautions using the hierarchy of control. Start at the top of the hierarchy (below) and only rely on lower-level controls like PPE when higher ones are not reasonably practicable — and document why. 6. Record the assessment. Write down the findings: the substances, the hazards, who is exposed, the controls chosen, who implements them and when the assessment will be reviewed. 7. Put the controls in place and maintain them. Fit the extraction, train the staff, and keep to the maintenance and testing duties — including Regulation 9 LEV testing (below). Monitor exposure where necessary under Regulation 10, and provide health surveillance where Regulation 11 requires it. 8. Review regularly. A COSHH assessment is a living document, not a filing exercise.

Workplace exposure limits and the 2026 enforcement picture

Workplace exposure limits (WELs) are published by HSE in EH40/2005 — the legal ceiling for how much of a substance a worker can breathe in over an 8-hour shift (the long-term limit) or a 15-minute period (the short-term exposure limit, or STEL).

Three things matter here:

• A WEL is a ceiling, not a target. Under Regulation 7(1), exposure must be *prevented* or, where that is not reasonably practicable, *adequately controlled*. Meeting the WEL does not automatically mean your controls are adequate.
• For carcinogens, mutagens and asthmagens (Schedule 6 substances), the duty is stricter. Exposure must be reduced to as low as is reasonably practicable — regardless of whether the WEL is met. Respiratory sensitisers have no "safe" threshold.
• Enforcement in 2026 is focused on exactly those substances. HSE's current inspection priorities centre on welding fume, respirable crystalline silica and isocyanates, and on the quality of assessments behind them.

Concrete examples of the current limits and positions:

• Respirable crystalline silica (RCS): 0.1 mg/m³ (8-hour average). From May 2026 HSE has made clear that uncontrolled dry cutting of engineered stone is unacceptable, and is running a 1,000-visit inspection programme through 2026/27 targeting engineered-stone fabricators.
• Welding fume: reclassified by the IARC as a Group 1 human carcinogen in 2017. HSE's safety bulletin STSU1/2019 requires rigorous controls even for mild steel — general ventilation alone is not enough.
• Isocyanates: a leading cause of occupational asthma, found in spray paints, foams and adhesives.

The hierarchy of control for hazardous substances

COSHH Regulation 7(1) requires you to work down this order, from most to least effective:

| Priority | Control | Example | | --- | --- | --- | | 1 | Eliminate | Remove the hazardous process entirely | | 2 | Substitute | Replace solvent-based paint with water-based; swap a powder for a liquid | | 3 | Enclose | Closed dispensing system for chemicals | | 4 | Local exhaust ventilation (LEV) | Extraction hood over a welding bench or nail-dust station | | 5 | General ventilation | Increased air changes across the room | | 6 | Safe systems of work | Reduced exposure time, permit-to-work, job rotation | | 7 | PPE — last resort | Respirators, gloves, goggles |

PPE is the last line of defence, not the first. If your assessment relies on PPE, you must be able to show why higher-level controls were not reasonably practicable — and the PPE must be the right type, fit-tested where required (RPE), and actually used.

LEV testing: the Regulation 9 duty

If you use local exhaust ventilation to control dust or fume, Regulation 9 requires you to keep it in efficient working order and have it thoroughly examined and tested by a competent person at least every 14 months. That interval is a statutory maximum with a small scheduling allowance — it is not an invitation to default every system to 14 months.

For high-risk processes listed in Schedule 4 of COSHH, the intervals are shorter:

• Every month: blasting in the cleaning of metal castings; jute cloth manufacture
• Every 6 months: processes giving off dust or fume in non-ferrous metal casting; grinding, abrading or polishing of metal articles (other than gold, platinum or iridium)

Test records must be kept for at least five years, and the record-keeping duty sits with the employer — outsourcing the test does not outsource the duty to act on the findings.

Health surveillance (Regulation 11)

Where exposure could cause an identifiable disease and there is a reasonable likelihood of it occurring, you must provide health surveillance — for example for workers exposed to isocyanates, flour dust, laboratory animal allergens, or substances that cause occupational dermatitis. Surveillance can be as simple as regular skin checks for dermatitis risks, or statutory medical surveillance for the most hazardous exposures. It exists to catch harm early, and it is a legal duty, not a perk.

Records, training and review

Regulation 12 requires you to provide employees with information, instruction and training — what the substances are, what the risks are, what controls are in place, and what to do in an emergency. Training must be repeated at suitable intervals and updated when the risk changes.

An assessment must be reviewed whenever there is reason to believe it is no longer valid — new substances, changed processes, new equipment, after an incident, or after monitoring shows exposure is creeping up. Many assessors work to a formal review at least every year or two; HSE's expectation is that review is triggered by change, not the calendar alone.

What happens if you don't comply?

HSE inspectors have wide powers. They can issue improvement notices (do this by a set date) and prohibition notices (stop this work now), serve information and inspection notices, and prosecute. COSHH breaches are triable either way:

• In the magistrates' court, fines can reach £20,000 per offence (or the statutory maximum for that offence)
• In the Crown Court, fines are unlimited

Beyond fines sit prohibition of your work, insurance consequences, civil claims from affected workers, and reputational damage. Inspectors routinely ask three questions: show me your assessment, show me your controls are working (including LEV test records), and show me your training records.

COSHH in hair and beauty salons

COSHH is not just a factory concern — it is one of the most commonly overlooked duties in salons, and HSE has specifically targeted the sector:

• Nail technicians: acrylates and methacrylates in gel polish and acrylic systems are powerful skin sensitisers; filing creates inhalable dust. Many local authorities now expect LEV or dust extraction at nail stations, not just a face mask.
• Hairdressers: persulphates in bleach powders are respiratory sensitisers and a known cause of occupational asthma; ammonia, hair dyes and straightening treatments containing formaldehyde add to the exposure picture.
• The fix: a product-by-product COSHH inventory, an SDS file, extraction or good ventilation, suitable gloves, and training so staff know what they are handling.

If you run a salon, the COSHH assessment sits alongside your fire risk assessment for nail and beauty salons — both are legal duties, and both will be examined if anything goes wrong.

How COSHH fits with your fire risk assessment

COSHH and fire safety overlap more than most businesses realise. The Regulatory Reform (Fire Safety) Order 2005 requires you to assess fire risk from the storage and use of flammable substances — which, under DSEAR, is assessed alongside your COSHH controls. A solvent store, an aerosol cage or a welding bay is a health hazard *and* a fire hazard, and your fire risk assessment must address the fire side just as your COSHH assessment addresses the health side. The responsible person under fire safety law is usually the same person with the COSHH duty — one inspection visit should satisfy both.

Frequently asked questions

1. What does COSHH stand for? COSHH stands for the Control of Substances Hazardous to Health Regulations 2002 (SI 2002/2677), the UK law requiring employers to prevent or adequately control worker exposure to hazardous substances.

2. Do I need a COSHH assessment if I only have two employees? Yes. COSHH applies to every employer and self-employed person, regardless of headcount. If the work could expose anyone — including the owner — to a hazardous substance, a suitable and sufficient assessment is required before work starts.

3. What is the difference between a WEL and the hierarchy of control? A workplace exposure limit (WEL) is the legal maximum airborne concentration in EH40/2005. The hierarchy of control is the required order for choosing controls — eliminate, substitute, enclose, LEV, ventilate, safe systems, then PPE. A WEL is a ceiling; the hierarchy is the route to getting below it.

4. How often should a COSHH assessment be reviewed? There is no fixed legal interval. The duty is to review whenever there is reason to believe the assessment is no longer valid — new substances, changed processes, new equipment, monitoring results or an incident. A formal review at least every 12–24 months is common practice.

5. How often must LEV be tested? Local exhaust ventilation must be thoroughly examined and tested by a competent person at least every 14 months — or every month or six months for the high-risk processes listed in Schedule 4 of COSHH. Records must be kept for at least five years.

6. Can I write my own COSHH assessment? Yes, if you have the competence — identify substances from SDSs, evaluate exposure, choose controls using the hierarchy, record and review. For complex or higher-risk work (welding fume, silica, isocyanates), it is worth having the assessment checked by a competent health and safety professional.

If you manage premises and need help getting your fire risk assessment right — the document that must sit alongside your COSHH records — book an assessment with HawkSwift or browse our compliance document bundles, which include a COSHH register and health and safety risk assessment templates.

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