What Is COSHH, and What Does It Actually Require?

Most COSHH guidance starts by telling you what the letters stand for and then lists duties. The more useful question is narrower: which of the things we actually use does this apply to? That is where the scoping facts matter — including the three substances everybody assumes are COSHH and are not.

Last reviewed: 20 September 2026 against HSE’s COSHH guidance (overview updated May 2026, assessment guidance updated July 2025).

What COSHH covers

HSE puts the duty simply: “The law requires you to adequately control exposure to materials in the workplace that cause ill health.”

That is broader than most people assume. COSHH covers dusts, gases, fumes, liquids, gels, powders and harmful micro-organisms, in materials ranging from paints and cleaners to flour dust and blood. Two consequences worth sitting with:

• Substances you create count, not just ones you buy. Welding fume, wood dust, silica dust from cutting, flour dust in a bakery — nobody delivered those in a labelled container, and they are some of the most damaging exposures there are.
• Biological agents count. Blood and body fluids, legionella in water systems, micro-organisms in waste handling or healthcare. Businesses that think “we don’t use chemicals” often have COSHH duties anyway.

What COSHH does not cover

Three substances are carved out because they have their own, stricter regimes. Assessing them under COSHH is a common and wasted effort — and, worse, it can mean the actual legal requirements go unmet.

If any of those three are present, stop and look at the right regulations. A COSHH assessment of asbestos is not compliance; it is a document that proves you looked in the wrong place.

The employer duties

How a COSHH assessment works

HSE’s steps for a COSHH assessment are:

1. Identify the hazards
2. Assess the risks
3. Control the risks
4. Review your controls

If that looks familiar, it should — it is the same shape as any other risk assessment, which is the point made below. When assessing the risk, HSE says to consider “how workers might be exposed (whether the substance can be breathed in, get onto or through the skin or can even be swallowed)”, along with how long and how often people are exposed, and what controls already exist.

The groups most often left out are the ones not doing the task: maintenance staff who open the machine afterwards, contractors who were not at your briefing, cleaners working after hours, and members of the public where they can be exposed. HSE names all of them.

How it fits with your general risk assessment

This is the question that confuses people holding two sets of paperwork. The answer is that a COSHH assessment is a specialisation, not a duplicate.

Your general risk assessment, required by the Management of Health and Safety at Work Regulations 1999, identifies that a hazard exists — “cleaning chemicals used daily”, “wood dust from the saw”. The COSHH assessment is where you work that hazard through in the detail COSHH demands: which substance, which route of exposure, who, how long, what control, what limit, what surveillance. Same method, narrower subject, more depth.

We set out the general method, and the other specialised assessments that hang off it, in workplace risk assessment. If you have not done that one, do it first — it tells you which specialised assessments you actually need.

Safety data sheets and labels

HSE’s starting instruction is practical: “Identify which substances are harmful by reading the product labels and safety data sheets (SDS). If in doubt, contact your supplier.”

A safety data sheet is free, your supplier must provide it for hazardous products, and sections 2, 7, 8 and 11 carry most of what an assessment needs — the hazards, safe handling and storage, exposure controls and personal protection, and the health effects. Two cautions:

• A safety data sheet is not a COSHH assessment. It describes the substance in general; your assessment describes what happens in your workplace, at your quantities, with your ventilation and your people. Filing a folder of SDS and calling it COSHH is the single most common mistake in this whole subject.
• It will not cover what you create. No supplier sends a data sheet for the wood dust your saw produces.

Controlling exposure, in order

COSHH requires you to prevent exposure where reasonably practicable, and only to control it where prevention is not. The order matters and is regularly inverted:

1. Eliminate — can the process be done without the substance at all?
2. Substitute — a safer substance, or the same one in a less hazardous form. A paste or pellet rather than a powder; a dilute solution rather than concentrate
3. Engineering controls — enclosure, local exhaust ventilation, automation
4. Organisational controls — fewer people exposed, shorter exposure, separation, procedures
5. Personal protective equipment — last, always. It protects one person, only while worn, only if it fits and only if it is the right type

Where a substance is a carcinogen, mutagen or asthmagen, the requirement is stricter still: exposure must be reduced as low as is reasonably practicable, not merely brought under a limit.

Workplace exposure limits

Some substances have a workplace exposure limit — a maximum concentration in the air, averaged over a reference period. They are published by HSE in EH40/2005 Workplace exposure limits, and this is worth being clear about: the limits in EH40 Table 1 are legally binding, because COSHH imposes its requirements by reference to them.

Two things follow. A limit is a ceiling, not a target — being under it does not mean exposure is adequately controlled if you could reasonably do better. And if you are relying on being under a limit, you need some basis for believing you are, which usually means air monitoring rather than an opinion.

Health surveillance

COSHH requires health surveillance where appropriate. Broadly, that means where there is an identifiable disease linked to the exposure, valid techniques for detecting it, a reasonable likelihood it could occur, and surveillance would benefit the worker. In practice it most often applies to skin (dermatitis) and lungs (occupational asthma), and to work with substances that have a workplace exposure limit.

It is not a general health check, and it is not optional where the conditions are met. If your assessment identifies a substance that causes asthma or dermatitis and people are exposed, surveillance is part of the answer.

Do we have to write it down?

HSE is explicit: “If you have 5 or more employees, you must record your assessment but, even if you have fewer than 5, it makes sense to write down what steps you have taken to identify the risks.”

The useful form is short and per-task rather than per-product: what is used, by whom, how, what could go wrong, what controls are in place, what to do in an emergency. An assessment organised around products tends to describe the bottle. One organised around tasks describes the exposure, which is what actually harms people.

Training

COSHH requires information, instruction and training — it does not name a qualification. What people need to know is what they are handling, how it could harm them, what the controls are for, how to use them, and what to do when something goes wrong.

A formal course earns its place for two groups: whoever writes the assessments, and supervisors who have to make judgements about whether a control is adequate. For everyone else, task-specific instruction from someone competent is often what the law is actually asking for.

Common mistakes

What this guide does not cover

It does not cover asbestos, lead or radioactive substances, which have their own regimes, nor DSEAR and explosive atmospheres, nor the transport or supply classification of chemicals. It is written for Great Britain. It describes the method rather than producing your assessments, which have to be specific to your substances and tasks.

COSHH training

Our Level 2 Principles of COSHH course covers the scope of hazardous substances in the workplace, the legislation around them, how they affect health, how to identify them, the control measures available, and the purpose and content of COSHH assessments. It runs to a minimum of three hours of training followed by a one-hour examination of 30 multiple-choice questions, and the certificate is valid for three years.

It sits alongside our wider health and safety courses, which include Levels 1 to 3, manual handling and risk assessment, as open course places and as group training at your premises for up to 12 people. For a group, the session can work through your own substances and your own tasks rather than generic examples.

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Frequently asked questions

What does COSHH stand for?

The Control of Substances Hazardous to Health Regulations 2002. They require employers to assess the risks from hazardous substances, prevent or control exposure, maintain the controls, provide information, instruction and training, carry out monitoring and health surveillance where appropriate, and plan for emergencies.

What substances does COSHH cover?

Dusts, gases, fumes, liquids, gels, powders and harmful micro-organisms — in materials ranging from paints and cleaners to flour dust and blood. It covers substances you create, such as welding fume and wood dust, as well as products you buy.

What is not covered by COSHH?

Lead, asbestos and radioactive substances. Each has its own regulations — the Control of Lead at Work Regulations, the Control of Asbestos Regulations, and the Ionising Radiations Regulations 2017. Assessing them under COSHH does not meet those requirements.

Is a safety data sheet the same as a COSHH assessment?

No, and this is the most common mistake in the subject. A safety data sheet describes the substance in general. A COSHH assessment describes your use of it — your quantities, your ventilation, your people, your tasks. A folder of data sheets is not compliance.

Do I have to write down a COSHH assessment?

If you have five or more employees, yes. HSE adds that even below five it makes sense to write down the steps taken to identify the risks. Organise it by task rather than by product — the task is what creates the exposure.

What are the steps of a COSHH assessment?

Identify the hazards, assess the risks, control the risks, review your controls. When assessing, consider how people might be exposed — breathing it in, skin contact or absorption, or swallowing it — along with how long and how often, and who else might be exposed.

What is a workplace exposure limit?

A maximum airborne concentration of a substance, averaged over a reference period. HSE publishes them in EH40/2005, and the limits in Table 1 are legally binding under COSHH. A limit is a ceiling rather than a target — exposure must still be adequately controlled.

Is COSHH training a legal requirement?

COSHH requires employers to provide information, instruction and training about the risks and the precautions taken. No particular qualification is named. A formal course is most valuable for whoever writes the assessments and for supervisors who judge whether controls are adequate.

How does a COSHH assessment relate to our general risk assessment?

It is a specialisation of it, not a duplicate. The general assessment identifies that a hazardous substance is in use; the COSHH assessment works that through in the detail COSHH requires. Do the general one first — it tells you which specialised assessments you need.

When is health surveillance required under COSHH?

Where it is appropriate: broadly, where there is an identifiable disease linked to the exposure, a valid way of detecting it, a reasonable likelihood it could occur, and a benefit to the worker. In practice it most often applies to skin and respiratory conditions such as dermatitis and occupational asthma.

Sources

• HSE, COSHH basics: overview
• HSE, How to carry out a COSHH risk assessment
• HSE, EH40/2005 Workplace exposure limits
• HSE, Control of substances hazardous to health (L5 Approved Code of Practice)

Not sure which of your substances need assessing, or who should be trained to write them? Call 0845 838 4643 or use the enquiry form on this page.