COSHH stands for Control of Substances Hazardous to Health
In full, the Control of Substances Hazardous to Health Regulations 2002. It is always written as an acronym and almost never expanded, which is why so many people work under it for years without ever being told what the letters mean.
What it requires is short to say and long to do: work out what in your work could harm somebody through exposure, and control it. The word doing the heavy lifting is exposure. COSHH is not about substances being dangerous in the abstract, it is about a substance getting into a person, and everything else in the regulations follows from that.
It is much broader than bottles with labels on
The commonest misunderstanding is that COSHH is about chemicals in containers. It is not. The HSE lists what counts, and most of the list has no label anywhere:
- Chemicals, and products containing chemicals.
- Fumes, including welding fume.
- Dusts, including silica from concrete and stone, and wood dust.
- Vapours and mists, from spraying, mixing and heating.
- Gases, including the asphyxiating ones that harm by displacing air rather than by being toxic.
- Biological agents, meaning germs. Leptospirosis and legionella both sit here.
- Nanotechnology.
Look down that list and notice how much of it is created by the work rather than delivered in a container. Nobody hands you a bottle of silica dust. It appears the moment somebody puts a disc into a paving slab, and it is the reason a site with no chemical store at all can still have a serious COSHH problem.
Three things COSHH does not cover, and people assume it does
This is the part almost nobody knows, and getting it wrong is worse than not knowing, because it means somebody has written an assessment that discharges no duty at all.
Asbestos and lead are outside COSHH because each has its own set of regulations, with their own duties around surveys, licensing, training, notification and medical surveillance. A COSHH assessment satisfies none of them.
Radioactive substances are outside it where being radioactive is the only thing that makes them hazardous. Where a substance is hazardous for a second reason as well, COSHH still applies to that part of it, which is the sort of distinction that sounds pedantic until it is your assessment being read.
Who has to do it, and there is no size threshold
Every employer whose work could expose somebody to a substance hazardous to health, and every self-employed person in the same position. There is no headcount at which the duty starts. A sole trader cutting kerbs is inside COSHH on the first cut.
Where a threshold does exist, it is about writing it down rather than about doing it, and confusing those two is the single most expensive error in this area. The COSHH assessment builder goes into exactly which duty is absolute and which one has the threshold, because that page is written for somebody who has to produce the document.
The word to remember is exposure
If you take one thing from this page: COSHH is not a rule about dangerous substances, it is a rule about people being exposed to them. That is why the same product can need a page of controls in one job and almost nothing in another, why the honest question is always what the work does rather than what the label says, and why a folder of manufacturer data sheets has never satisfied anybody who knew what they were looking at.
Common questions
Does COSHH cover asbestos?
No. Asbestos has its own regulations, its own licensing regime, its own training requirements and its own notification duties, none of which a COSHH assessment satisfies, and that is the exclusion that matters most on a construction site. If you suspect asbestos, a COSHH assessment is not the document you need and filling one in does not discharge anything. Stop, and get a refurbishment and demolition survey.
Is a safety data sheet the same as a COSHH assessment?
No, and treating it as one is the commonest mistake in this whole area. A safety data sheet is written by the manufacturer about the PRODUCT, in general, for every possible user. A COSHH assessment is written by you about the WORK: this substance, this quantity, in this space, with this ventilation, for this long. The data sheet is an input to the assessment and is never a substitute for it. A file of printed data sheets is not a COSHH assessment and will not be accepted as one.
Is a COSHH assessment separate from a risk assessment?
It is a specific assessment sitting inside your general duty to assess risk. In practice most people keep them as separate documents, because a COSHH assessment carries things a general one has no field for: the substance, the route into the body, the exposure, the controls that stop it. A principal contractor asking for both is not asking twice for the same thing.
Does COSHH apply to ordinary household products?
At work, yes. The regulations are about the substance and the exposure, not about where you bought it, so bleach, adhesives, cleaning products and fuel are all inside COSHH when they are used for work. What changes is the assessment rather than whether one is needed: an occasional wipe with a household cleaner is a very short assessment, and the same product used all day in an unventilated room is not.
Does COSHH cover dust from cutting and drilling?
Yes, and dust is where COSHH bites hardest on site while being thought about least. Nothing arrives in a labelled container: the hazard is created by the work itself, when somebody cuts a paving slab, chases a wall or sands a floor. Silica dust from concrete, stone and mortar is the serious one, and wood dust is a close second. Neither has a hazard symbol on it anywhere, which is exactly why both get missed.
Does COSHH still apply if the work is outdoors?
Yes. Outdoors reduces exposure, often dramatically, and reducing exposure is what the assessment is for rather than a reason to skip it. It also does not help nearly as much as people assume for anything generated close to the face, because the dust cloud from a cut-off saw sits in your breathing zone whether there is a roof over it or not. Outdoors is a control, and controls belong in the assessment.