COSHH stands for the Control of Substances Hazardous to Health Regulations 2002, the law that requires employers to control workers' exposure to substances that can harm their health. On a building site that means things like dust, fumes, cement, solvents and some paints and adhesives. This article is independent study material, it is not affiliated with CSCS or CITB, and it explains the idea in plain English rather than quoting the regulations.
Key takeaways
- COSHH is the Control of Substances Hazardous to Health Regulations 2002, and its purpose is to prevent ill health caused by hazardous substances at work.
- Hazardous substances include chemicals, fumes, dusts, vapours and mists, and COSHH also covers biological agents.
- Employers must assess the risk, decide what controls are needed and make sure those controls are used and kept working.
- Workers must use the controls provided, follow instructions and training, and report problems.
- Asbestos and lead are covered by their own specific regulations, so they are not handled under COSHH in the same way.
- The product label and the supplier's safety data sheet are your first source of information about a substance.
What COSHH means
Regulation 7(1) of the Control of Substances Hazardous to Health Regulations 2002 requires employers to prevent their employees' exposure to substances hazardous to health or, where that is not reasonably practicable, to control it adequately. HSE's COSHH page is the official starting point for guidance. In practice, the idea is simple: find out what substances are present, work out how they could harm people, and put controls in place so that exposure is prevented or, where that is not possible, adequately controlled.
Ill health from substances is often slow and quiet. A cut shows straight away, but breathing in a harmful dust day after day may not cause obvious symptoms until much later. That is why COSHH treats exposure as something to be controlled in advance, not something to wait and see about.
Which substances does it cover?
COSHH is about substances that can harm health. These can enter the body in several ways: by breathing them in, by skin contact, through the eyes, by swallowing, or through broken skin. Hazardous substances on construction sites commonly include:
- Dusts produced when cutting, drilling, sanding or demolishing materials.
- Wet cement and other products that can irritate or burn the skin.
- Solvents, paints, adhesives and sealants that give off vapours.
- Fumes from processes such as welding or from engines in confined areas.
- Biological agents, for example from contaminated water or waste, where relevant.
Not everything is handled under COSHH. Asbestos and lead have their own specific regulations, so if you suspect either is present you should stop and report it rather than treat it as an ordinary COSHH substance. Check the HSE pages for the current rules on each.
What employers must do
The Control of Substances Hazardous to Health Regulations 2002 set out the duties of employers, including those in regulations 6, 7, 10 and 11. In plain English, an employer has to:
- Find out what hazardous substances are present and how they could harm people.
- Decide how to prevent harm and put the right control measures in place.
- Make sure the control measures are used and kept in good working order.
- Give workers the information, instruction and training they need.
- Provide monitoring and health surveillance where it is appropriate.
- Plan for emergencies, such as spills or accidental exposure.
Wherever possible, the aim is to prevent exposure altogether, for example by using a less hazardous product or a different method. Where exposure cannot be avoided, controls such as extraction, water suppression or enclosure come before personal protective equipment, which is the last line of defence. If you want to see how that order works, the site safety terms overview covers the hierarchy of control.
Reading labels and safety data sheets
Suppliers of hazardous products label them with warning information and provide a safety data sheet that describes the hazards, safe handling, storage, first aid and what to do in a spill. These documents feed into the employer's COSHH assessment, so they are not just paperwork. If a product arrives in an unlabelled container, or the label is damaged or unreadable, do not guess what it is. Stop and ask your supervisor, because you cannot control a risk you cannot identify. Likewise, never decant a product into an unmarked bottle or drink container.
What workers must do
COSHH is not only an employer's duty. As a worker, you are expected to:
- Use the control measures you have been given, such as extraction or water suppression, and do not bypass them.
- Wear the personal protective equipment you have been provided with, and wear it properly.
- Follow the instructions and training you receive.
- Keep to hygiene rules, such as washing before eating and not eating or smoking in contaminated areas.
- Return and store equipment and substances correctly.
- Report faults, damage, spills and any health symptoms that may be related to your work.
If you are not sure how to use a product safely, stop and ask your supervisor before you start. For more on everyday site practice, see COSHH basics.
Checklist before using a substance
- [ ] Have I read the product label?
- [ ] Is there a safety data sheet from the supplier, and have I been told what it says?
- [ ] Do I know what controls are required, such as ventilation or extraction?
- [ ] Do I have the right protective equipment, and does it fit?
- [ ] Do I know what to do in a spill or an exposure?
- [ ] Do I know how to store and dispose of the substance and its containers?
How COSHH may appear in practice questions
Practice questions on this site about COSHH focus on the principle rather than the legal detail. Typical themes in our questions include reading labels and safety data sheets, reporting a spill, choosing a control that removes the hazard rather than relying on a mask, and knowing that the employer must provide information and training. A good rule of thumb for study is: find out what the substance is, prevent exposure where you can, control it where you cannot, and report anything that goes wrong. Always check the official CITB pages for the current test format, since this site is independent.
You can try applying these ideas to scenarios on the free practice questions page. Practice scores are not an official result.
A worked example: a dusty cutting job
This is a made-up scenario to show how the COSHH idea works on a real task. It illustrates the way of thinking and is not a substitute for the site's own assessment.
A small team has to cut through masonry to fit a new opening. Cutting masonry creates dust, and dust is one of the hazardous substances this article lists. Here is how the sequence might run.
- Identify. Before anyone picks up a tool, the supervisor asks what is being cut and what dust it will produce. The answer comes from the site's assessment, the material information and the supplier's data where there is any, not from guesswork.
- Prevent if possible. Could the job be done a different way that makes less dust, or at a different place, such as cutting off site? Prevention comes first because it removes the problem instead of managing it (general practice).
- Control what remains. If the cutting must happen on site, controls such as water suppression or extraction at the tool come before relying on a mask. This follows the order described earlier in the article, where protective equipment is the last line of defence.
- Protect with equipment. Where a risk remains, the team uses the protective equipment they have been given, fitted and used as instructed.
- Keep controls working. The water supply is checked, the extraction is switched on and the equipment is kept in good order. A control that is switched off or blocked is not a control.
- Look after hygiene. The team wash before eating and do not eat in the dusty area.
- Report. Anyone who sees a fault, a spill or a health symptom that might be linked to the work tells the supervisor.
The example shows why COSHH is described as a process, not a single rule. Each step feeds the next, and the worker's part is to use the controls, follow the instruction and speak up.
What to check first on site
Workers often meet a substance before they meet the paperwork. These "what to check first" prompts help you act sensibly in the moment. They are general practice, and the site's own assessment and your supervisor are the authority for your task.
| Situation | What to check first |
|---|---|
| A new product arrives on site | Read the label and ask for the safety data sheet and the site's assessment |
| The label is missing or unreadable | Stop and ask your supervisor, and do not guess or decant it |
| You are about to cut, sand or drill | Ask what dust the material makes and what control is required |
| A control is switched off or broken | Stop the task, report it and do not bypass it |
| You see a spill | Follow the spill instruction from the data sheet and tell your supervisor |
| You think a material could be asbestos or lead | Stop and report it, as these have their own regulations |
| You feel unwell after a task | Tell your supervisor and report the symptoms |
Two ideas run through the table. First, identify before you act, because you cannot control what you cannot name. Second, stop and ask when you are unsure, because asking costs a minute while a wrong guess may cost your health.
For everyday habits that go with this, read COSHH basics. For the wider vocabulary behind terms like hierarchy of control, the site safety terms overview is a companion guide. For the legal text and official guidance, use the HSE and Legislation.gov.uk pages in the sources below.
FAQ
What does COSHH stand for?
COSHH stands for the Control of Substances Hazardous to Health. The Regulations in force are the Control of Substances Hazardous to Health Regulations 2002, which require employers to protect workers from exposure to harmful substances.
Does COSHH only apply to chemicals?
No. COSHH covers chemicals, but also dusts, fumes, vapours and mists, and biological agents. Many construction hazards, such as dust from cutting materials, fall under it even though they are not chemicals in a tin or bottle.
Is wearing a mask enough to comply with COSHH?
Usually not. Personal protective equipment is a last resort, used when other controls cannot remove the exposure. Employers should first try to prevent exposure or control it at source, then use protective equipment where a risk remains.
Where do I find information about a substance?
Start with the label, then the supplier's safety data sheet, and ask your supervisor for the site's COSHH assessment. For the law and official guidance, use the HSE and Legislation.gov.uk pages listed in the sources below.
Sources
- HSE: COSHH (Control of Substances Hazardous to Health)
- Legislation.gov.uk: Control of Substances Hazardous to Health Regulations 2002
Independent guide, not affiliated with, authorised by, approved by or endorsed by CSCS or CITB. Last updated 2026-10-08.