What Is Covered by COSHH? Scope, Substances, and Exceptions

The Short Answer

COSHH covers almost every hazardous substance you will encounter at work — chemicals, dust, fumes, vapours, mists, gases, and biological agents. If a substance can harm someone's health through exposure at work, it probably falls under the Control of Substances Hazardous to Health Regulations 2002.

Lead, asbestos and radioactive substances are the main exceptions — but they are not simply "outside COSHH". Regulation 5(1) switches off only regulations 6 to 13, and only where and to the extent that the other regime applies. Everything else is COSHH territory.

The rest of this guide helps you work out which specific substances in your workplace need a COSHH assessment — and which do not.

Substances Covered by COSHH

The COSHH Regulations 2002 define a "substance hazardous to health" broadly. The HSE groups them into three main categories.

1. Commercial Chemical Products

Any product you buy that carries a GHS hazard label is a COSHH substance. This includes:

Cleaning products — bleach, degreasers, descalers, disinfectants, sanitisers
Paints, varnishes, and coatings — solvent-based and some water-based formulations
Adhesives and sealants — epoxy resins, cyanoacrylates, contact adhesives
Solvents — acetone, white spirit, IPA, toluene, methylene chloride
Salon products — hair colour containing PPD, bleach powder with persulphates, perm solutions
Agricultural chemicals — pesticides, herbicides, fertilisers
Fuels — diesel, petrol (primarily an inhalation risk during decanting)
Metalworking fluids — cutting oils, coolants (both neat and water-mix)

The Safety Data Sheet (SDS) from the manufacturer tells you exactly what hazards each product presents. If you do not have an SDS for a product, ask your supplier — they must provide one free of charge under the REACH regulation. For help interpreting an SDS, our guide on how to do a COSHH assessment explains which sections matter most.

2. Substances Generated by Work Processes

COSHH does not only cover things that arrive in a bottle. If your work creates a hazardous substance as a by-product, that substance needs assessing too. This catches many businesses off guard.

Dust:

Dust type	Generated by	Key hazard	WEL (8-hr TWA)
Respirable crystalline silica	Cutting, drilling, grinding concrete, brick, stone	Silicosis, lung cancer (IARC Group 1)	0.1 mg/m³
Hardwood dust	Cutting, sanding, routing oak, beech, ash, mahogany	Nasal cavity cancer, asthma	3 mg/m³
Softwood dust	Cutting, sanding pine, spruce, cedar	Asthma, respiratory irritation	5 mg/m³
Flour dust	Milling, baking, mixing	Occupational asthma ("baker's asthma")	10 mg/m³ (inhalable)
Grain dust	Handling, transporting, processing grain	Respiratory sensitisation	10 mg/m³ (inhalable)

Yes — dust is covered by COSHH. This is one of the most common questions employers ask, and the answer is unequivocal. If your process generates airborne dust that can be inhaled, it needs a COSHH assessment regardless of whether the raw material came with a hazard label.

Fumes:

Welding fume — generated by MIG, TIG, MMA, and gas welding. The HSE reclassified all welding fume (including mild steel) as a carcinogen in 2019. Indoor welding now needs engineering controls, typically LEV — with a narrow exception for genuinely sporadic welding (less than once a week, under an hour each time), where HSE accepts RPE plus good general ventilation.
Soldering fume — rosin-based flux generates colophony fume, a respiratory sensitiser that can cause occupational asthma.
Diesel exhaust emissions (DEE) — classified as a Group 1 carcinogen by the IARC. Relevant to any workplace where diesel vehicles operate in enclosed or semi-enclosed spaces.

Other process-generated substances:

Rubber fume — from rubber mixing, moulding, and vulcanisation
Oil mist — from metalworking, machining, and lubrication systems
Cement dust — Portland cement contains hexavalent chromium (Cr(VI)), a skin sensitiser

3. Biological Agents

Bacteria, viruses, fungi, and other micro-organisms are covered if they present a health risk in your workplace. This applies to:

Healthcare and dental settings (blood-borne viruses, airborne pathogens)
Waste management and recycling (bioaerosols, leptospirosis from rat urine)
Agriculture and veterinary work (zoonotic infections, organic dust)
Laboratories (cultured micro-organisms)
Water systems (legionella bacteria — though this also falls under L8 guidance)
Food processing (moulds, biological contamination)

Biological agents are classified into four hazard groups depending on severity and transmissibility. Group 1 is unlikely to cause disease; Group 4 causes severe disease with no effective treatment. Your COSHH assessment should identify the hazard group and the controls appropriate to that level.

What Is NOT Covered by COSHH (and What Only Partly Steps Aside)

Three categories of hazardous substance are dealt with mainly by their own regulations. The mechanism matters, because it is narrower than it is usually described. Regulation 5(1) disapplies regulations 6 to 13 — assessment, prevention and control, maintenance of controls, monitoring, health surveillance, training, and emergency arrangements — and it does so only "where and to the extent that" the other regime applies. The rest of COSHH (regulations 1 to 5 and 14 to 19, including the regulation 4 prohibitions on certain substances) continues to apply throughout.

Note also that only two of the three are named in COSHH at all:

Substance	Dealt with by	How COSHH steps back
Lead	Control of Lead at Work Regulations 2002	Named in regulation 5(1)(a)(ii). Regulations 6 to 13 are disapplied where and to the extent that CLAW 2002 applies — relevant to smelting, battery manufacture, demolition of painted surfaces and stained glass.
Asbestos	Control of Asbestos Regulations 2012	Named in regulation 5(1)(a)(iii), on the same "to the extent that" basis. Work that could disturb asbestos-containing materials needs a separate management survey and risk assessment.
Radioactive substances	Ionising Radiations Regulations 2017	Not named in COSHH — search the instrument for "ionising" and you get no hits. Regulation 5(1)(b) works by property instead, disapplying regulations 6 to 13 where a substance is hazardous to health "solely by virtue of its radioactive, explosive or flammable properties". IRR 2017 governs the radiation risk, but it is not what does the excluding.

If you work with any of these, you need an assessment under the specific regulations. But keep the two limits in view. Only regulations 6 to 13 step back, and only to the extent that the other regime applies. A substance that is both radioactive and chemically toxic — many uranium and thorium compounds, and much naturally occurring radioactive material — is not hazardous solely by virtue of its radioactivity, so it keeps its COSHH assessment for the chemical risk. The same logic covers a lead-bearing product that is also, say, a skin sensitiser: CLAW 2002 does not reach the sensitisation, so COSHH still does.

Also not covered by COSHH:

Substances that present only a physical hazard (fire, explosion) but no health hazard — these fall under fire safety or DSEAR (Dangerous Substances and Explosive Atmospheres Regulations 2002)
Noise and vibration — covered by the Control of Noise at Work Regulations 2005 and the Control of Vibration at Work Regulations 2005
Ergonomic hazards, temperature extremes, and general workplace hazards — covered under the general duties in the Health and Safety at Work Act 1974

How to Decide If Something Needs a COSHH Assessment

Use this decision framework for any substance in your workplace:

Step 1 — Does it have a hazard label or SDS? If yes → it is a COSHH substance. Assess it.

Step 2 — Does your process generate dust, fume, vapour, or mist? If yes → the airborne substance is covered by COSHH, even if the raw material is harmless. Cutting MDF (a safe product) creates hardwood dust (a carcinogen). Assess the dust, not just the board.

Step 3 — Could workers be exposed to biological agents? If yes (healthcare, waste, agriculture, water systems) → COSHH applies. Assess the biological risk.

Step 4 — Is it lead, asbestos, or radioactive? If yes → assess it under the relevant specific regulations. But do not stop there: regulations 6 to 13 step back only to the extent that that regime applies, so if the substance also carries a separate chemical health risk (radioactive and toxic, lead and sensitising) those regulations still bite. The rest of COSHH applies either way.

Step 5 — Is the only hazard physical (fire, explosion) with no health risk? If yes → not COSHH. Covered by DSEAR or fire safety regulations.

If you are still unsure, the safe assumption is to assess it under COSHH. Over-assessing costs you time; under-assessing can cost you a prosecution.

Industry-Specific Examples

Cleaning Companies

Every cleaning product you use is a COSHH substance — bleach, degreasers, toilet cleaners, floor polish, disinfectants. Contract cleaners often handle 15-20 different products. See our full COSHH guide for cleaning companies for substance-by-substance detail.

Hairdressing Salons

Hair colour (PPD), bleach powder (persulphates), perm solutions (thioglycolates), keratin treatments (potential formaldehyde release), and cleaning products all require assessment. Our COSHH guide for hairdressers covers the specific risks.

Construction Sites

Silica dust, cement, welding fume, wood dust, solvents, adhesives, paints, and coatings. Construction generates more variety of COSHH substances than almost any other sector. Even demolition work can release legacy contaminants.

Offices

Offices often assume COSHH does not apply to them. In reality, cleaning products, printer toner, correction fluid, and any chemicals used by maintenance staff all need assessing. The assessments are typically short and straightforward — but they still need to exist.

Schools

Science lab chemicals, cleaning products, art supplies (some contain solvents or fixatives), caretaker maintenance products, and substances generated by DT workshops (wood dust, soldering fume). Schools have a duty of care to both staff and pupils.

Common Scope Mistakes

"We only use small quantities, so COSHH doesn't apply." — Wrong. There is no quantity threshold. A single bottle of bleach needs a COSHH assessment.

"The product isn't labelled as hazardous, so it's fine." — Not necessarily. Some products are hazardous in use even if the product itself is not classified (e.g., cutting a non-hazardous material that generates hazardous dust). Also check for unlabelled decanted products — the original product may have been hazardous.

"We've been using it for years with no problems." — Many COSHH health effects (occupational asthma, dermatitis, cancer) develop over years of exposure. Absence of symptoms does not mean absence of risk.

"Our supplier said it's safe." — The SDS is the definitive source. Sales claims and marketing materials are not a substitute for the manufacturer's hazard data.

Getting Started

If you have not assessed your COSHH scope yet:

Walk through every area of your workplace and list every substance — in bottles, generated by processes, and biological risks.
Collect the SDS for every commercial product.
Check whether any of your substances are excluded (lead, asbestos, radioactive) and need their own specific assessment.
For everything else, write a COSHH assessment. Our free COSHH assessment template gives you the structure, and our 3 worked examples show what a completed assessment looks like.
Not sure where your compliance stands overall? Use our free COSHH Compliance Checker to get a quick score in under 2 minutes.

Making COSHH Scope Manageable

For many small businesses, the sheer scope of COSHH feels overwhelming — especially once you realise process-generated substances count too. But the assessment itself does not have to be complicated. A straightforward low-risk substance might take 15 minutes to assess.

COSHHmate is being built to make this process faster. You will get a guided assessment builder that walks you through every required field, an automatic chemical register that grows as you add substances, and email reminders before review dates. Flat monthly pricing — no per-user fees.

If you want to take the guesswork out of COSHH compliance, join the waitlist to be first to know when COSHHmate launches.

This is general guidance based on the COSHH Regulations 2002 and published HSE guidance. Verify the requirements for your specific substances and processes against HSE guidance. Not legal or safety advice.