How to Do a COSHH Assessment: 8-Step Guide for UK Employers

How to Do a COSHH Assessment (Short Answer)

A COSHH assessment is a written record that identifies every hazardous substance in your workplace, evaluates the health risks, and documents the controls you have in place. You are legally required to complete one under the Control of Substances Hazardous to Health Regulations 2002.

The process takes 15-30 minutes per substance once you know what you are doing. Here are the 8 steps.

Step 1 — List Every Hazardous Substance

Walk through your workplace — every room, cupboard, workshop, vehicle, and storage area. Write down every chemical product you use, store, or create during your work.

Do not limit yourself to bottled chemicals. COSHH covers:

Commercial products (cleaners, paints, adhesives, solvents)
Substances generated by your processes (wood dust, welding fume, flour dust, diesel exhaust)
Biological agents (bacteria, moulds, viruses in healthcare or waste handling)

A cleaning company might list 15-20 products. A manufacturing workshop might have 30-50. A hairdressing salon typically has 10-15.

Tip: Check the COSHH cleaning cupboard, under sinks, in vehicles, and in any "someone left this here" corners. Forgotten products still need assessing.

Step 2 — Collect the Safety Data Sheets

For every commercial chemical product, you need the manufacturer's Safety Data Sheet (SDS). This is the document that tells you exactly what hazards the product presents and how to handle it safely.

Your supplier must provide an SDS free of charge — it is a legal requirement under the REACH regulation. If you are missing any, email your supplier and request the current version. Most suppliers now have them downloadable from their website.

An SDS has 16 sections. The ones you will use most in your COSHH assessment are:

Section 2 — Hazard identification (GHS pictograms, signal words, H-phrases)
Section 4 — First-aid measures
Section 7 — Handling and storage
Section 8 — Exposure controls and PPE recommendations
Section 11 — Toxicological information

Keep your SDS collection organised. You will need to reference them during HSE inspections and whenever you review your assessments.

Step 3 — Identify the Hazards

For each substance, record the specific hazards from the SDS and product label. Use the GHS hazard classification system:

| Hazard type | Examples | GHS pictogram | |-------------|----------|---------------| | Acute toxicity | Methanol, certain pesticides | Skull and crossbones | | Skin/eye irritation | Many cleaning products, solvents | Exclamation mark | | Corrosive | Bleach, strong acids, caustic soda | Corrosion | | Respiratory sensitiser | Isocyanates, flour dust, wood dust | Health hazard | | Flammable | Acetone, white spirit, aerosols | Flame | | Carcinogenic | Certain hardwood dusts, benzene | Health hazard |

Record the H-phrases (hazard statements) from the label. These give specific information — for example, H314 means "causes severe skin burns and eye damage" while H317 means "may cause an allergic skin reaction."

Step 4 — Decide Who Could Be Harmed and How

Think about every person who might be exposed to the substance:

Employees using the product directly — the cleaner spraying the degreaser, the joiner cutting MDF
Colleagues working nearby — the office worker whose desk is near the workshop
Contractors and visitors — delivery drivers, maintenance workers, clients
Vulnerable groups — pregnant workers, young workers, anyone with asthma or skin conditions

For each group, identify the route of exposure:

Inhalation — breathing in vapour, mist, fume, or dust
Skin contact — direct contact or splashes
Eye contact — splashes or airborne particles
Ingestion — accidental swallowing (more common than you might think, especially when food and chemicals share spaces)

Be specific. "Staff could be exposed" is not enough. "Cleaners are exposed to bleach vapour by inhalation when cleaning bathrooms with limited ventilation, typically for 20 minutes per room, 4 rooms per shift" tells you something useful.

Step 5 — Evaluate Your Current Controls

Document every control measure you already have in place. The COSHH hierarchy of control runs from most effective to least effective:

Elimination — Can you stop using the substance entirely? Switch to a non-hazardous alternative?
Substitution — Can you use a less hazardous version? (e.g., water-based paint instead of solvent-based)
Engineering controls — Local exhaust ventilation (LEV), enclosed processes, automated dispensing
Administrative controls — Safe working procedures, restricted access, training, exposure time limits
PPE — Gloves, goggles, respirators, aprons (always the last resort, never the only control)

For each control, note whether it is actually being used consistently. A ventilation system that nobody switches on is not a control. Gloves in a cupboard that nobody opens are not PPE.

Step 6 — Check Against Workplace Exposure Limits

Some substances have Workplace Exposure Limits (WELs) — legal maximum concentrations in the air, measured over 8 hours (TWA) or 15 minutes (STEL). You can find these in the HSE's publication EH40.

If your substance has a WEL, you need to consider whether your workers could be exposed above that limit. For many SME situations — using cleaning products in ventilated rooms, handling small quantities of paint — you can make a reasonable judgement without air monitoring. But if you are using volatile solvents in enclosed spaces, generating significant dust, or handling large quantities, you may need to arrange professional exposure monitoring.

If monitoring shows exposure above the WEL, you must take immediate action to reduce it.

Step 7 — Determine Whether Health Surveillance Is Needed

For certain substances, you are legally required to put exposed workers under health surveillance. This applies when:

Workers are exposed to substances known to cause occupational asthma (isocyanates, flour dust, wood dust, latex, certain adhesives)
Workers handle substances that cause occupational dermatitis with repeated skin contact
Workers are exposed to substances with specific medical surveillance requirements (lead, certain pesticides)

Health surveillance might mean regular skin checks by a trained supervisor, lung function testing by an occupational health professional, or blood tests for specific substances. If you are unsure whether health surveillance applies, the HSE's COSHH health surveillance guidance is the definitive source.

Step 8 — Record, Communicate, and Set a Review Date

Write everything down in a structured format. Your completed assessment must be accessible to every worker who could be exposed to the substance. This matters because an HSE inspector will ask to see your assessments, and they will also ask your staff whether they know what the assessments say.

Set a review date. The law does not specify an exact interval, but the HSE recommends reviewing at least annually. You should also review whenever:

You change products, quantities, or suppliers
You change your work process or equipment
Someone reports symptoms (skin irritation, breathing problems)
An incident or near-miss occurs
New information becomes available about the substance's hazards

Keep a record of every review, even if the assessment has not changed. "Reviewed 15 March 2026 — no changes required" is a valid review note that proves you are actively managing the risk.

What a Finished COSHH Assessment Looks Like

Here is a summary of every field your assessment should cover:

Substance name and supplier
SDS reference and date
Hazard classification (pictograms, H-phrases, signal words)
Where and how the substance is used (tasks, quantities, frequency)
Who is at risk and how (roles, exposure routes, duration)
Current control measures (following the hierarchy)
Workplace exposure limits (if applicable)
Health surveillance requirements (if applicable)
Emergency procedures (first aid, spill response)
Conclusion — are current controls adequate, or is further action needed?
Action plan (if controls are inadequate) — what, who, by when
Assessment date and assessor name
Review date

If you want to see a worked example with real substances, read our COSHH risk assessment example guide with three complete walkthroughs.

Common Mistakes That Catch People Out

Copying a generic template without tailoring it. Your assessment must reflect your specific workplace, your specific products, and your specific tasks. An inspector can spot a generic copy-paste immediately.

Forgetting process-generated substances. Wood dust, welding fume, flour dust, and engine exhaust are all COSHH substances — they do not come in a bottle, but they still need assessing.

Relying on PPE as the primary control. PPE should be the last line of defence, not the first. If your assessment says "wear gloves" without considering ventilation, substitution, or process changes, it is not following the hierarchy of control.

Not reviewing on time. An overdue assessment is almost as bad as having none. The HSE expects active, ongoing management — not a one-off exercise.

Not communicating findings to staff. An assessment locked in a filing cabinet is not protecting anyone. Every worker who could be exposed needs to know the hazards and the controls.

For more detail on these pitfalls, see our COSHH risk assessment examples.

Paper vs Digital: Which Approach Works?

Word documents and paper forms are fine for a small operation with a handful of substances. But they break down quickly as your business grows:

You end up with multiple versions of the same assessment across different folders
Nobody remembers when reviews are due
New starters never see the assessments that apply to their work
Your chemical register (if you even have one) lives in a separate spreadsheet

COSHHmate replaces all of this with a single system. You get a guided assessment builder that walks you through every required field, an automatic chemical register across all your sites, email reminders before review dates, and instant PDF export when an inspector asks to see your paperwork.

Pricing is a flat monthly fee — no per-user charges. A team of five costs the same as a team of one.

If you are ready to get your COSHH assessments properly organised, create a free account and complete your first assessment in under 10 minutes.