COSHH Symbols
Nine pictograms, each a red-bordered diamond, tell you what a substance can do to you before you open it. They come up throughout the CITB HS&E test, and on site they are the difference between reading a label and reading a label properly.
They are not actually COSHH symbols
Everyone calls them COSHH symbols, including most revision sites, but HSE calls them GB CLP hazard pictograms. They come from the classification, labelling and packaging rules, which govern what goes on the product label. COSHH is the separate set of regulations that governs what you have to do about a hazardous substance: assess it, control exposure, and check the controls still work.
The distinction matters for one practical reason. The pictogram tells you the substance is dangerous. It does not tell you the safe method, the exposure limit or the protection you need. Only the COSHH assessment does that.
All nine pictograms and their meanings
HSE describes the pictograms as appearing "in the shape of a diamond with a distinctive red border and white background". More than one can appear on a single product.
| Pictogram | Symbol | What it is warning you about |
|---|---|---|
| Explosive | Exploding bomb | The substance can explode. On site this is most often cartridges for nail guns and similar powder-actuated tools. |
| Flammable | Flame | It catches fire easily. Solvents, adhesives, LPG, petrol for cut-off saws and most aerosols carry this one. |
| Oxidising | Flame over circle | It feeds a fire, so a fire near it burns harder and faster. It does not have to burn itself to be dangerous. |
| Corrosive | Corrosion | It attacks skin, eyes and metal. Wet cement and concrete are the classic construction example and cause serious burns. |
| Acute toxicity | Skull and crossbones | A small dose can kill or make you seriously ill quickly. This is the pictogram for harm that arrives fast, as opposed to the serious health hazard symbol, which is for harm that arrives years later. |
| Hazardous to the environment | Environment | It harms the aquatic environment. This is the one pictogram that does not bring a substance under COSHH at all, because COSHH covers the health hazard classes only. Spill and waste duties come from environmental law instead. |
| Health hazard, or hazardous to the ozone layer | Exclamation mark | Less severe effects such as skin or eye irritation, or damage to the ozone layer. Easy to dismiss, which is why dermatitis is so common in the trades. |
| Serious health hazard | Health hazard | Long-term effects such as cancer, damage to fertility, organ damage or breathing sensitisation. Many resins, sealants and two-pack systems carry it. |
| Gas under pressure | Gas cylinder | The container is pressurised and can burst or rocket if it is heated or damaged. Oxygen, acetylene and propane cylinders. |
The three that catch construction workers out
- Corrosive, on wet cement. Cement is the corrosive substance people are most likely to handle with bare hands. HSE is blunt about what it does: wet cement is highly alkaline, and a serious burn or ulcer can develop rapidly where it is trapped against the skin, inside a boot or a glove cuff.
- Serious health hazard, on the products you open. Resins, sealants and two-pack systems carry this one, and it warns about harm that shows up years later rather than today. Note that construction dust you create by cutting carries no pictogram at all, because nobody supplied it to you in a labelled container. It is no less dangerous for that.
- Gas under pressure, on cylinders. The contents may be harmless. The pressure is not, and a damaged cylinder can travel far enough to kill someone at the other end of the site.
How this is examined
Questions in this area rarely ask you to name a pictogram. They put you in a situation: you are handed a container carrying a symbol and asked what you do next. The answer is almost never "carry on carefully" and almost always "check the COSHH assessment first", because the assessment is what names the control measures.
Note also that PPE against substances hazardous to health sits under COSHH rather than under the PPE at Work Regulations, which is a favourite distinction in the Specialist papers.
Practise the COSHH questions
Drill the hazardous substances bank with written explanations, or sit a full mock to see whether this topic is actually where you are dropping marks.
The nine pictogram names, their symbols and the red diamond description are transcribed from HSE's hazard pictograms page under hse.gov.uk/chemical-classification, checked August 2026. What each pictogram covers is taken from the hazard classes in Annex V of the CLP Regulation on legislation.gov.uk, which is also the source for the environment pictogram sitting outside COSHH: regulation 2(1) of COSHH 2002 reaches the health hazard classes only. The wet cement description comes from HSE's cement page under hse.gov.uk/construction. Substance examples beyond cement are ours, chosen for construction relevance, and no product is named as carrying a specific pictogram unless its label says so.
COSHH symbols: common questions
- How many COSHH symbols are there?
- Nine. HSE's gallery of GB CLP hazard pictograms lists explosive, flammable, oxidising, corrosive, acute toxicity, hazardous to the environment, health hazard or hazardous to the ozone layer, serious health hazard, and gas under pressure.
- Are COSHH symbols and hazard pictograms the same thing?
- They are the same pictures, but the name is wrong. HSE calls them GB CLP hazard pictograms, and they come from the classification, labelling and packaging rules. COSHH is a separate set of regulations covering what you must do about substances hazardous to health. People say COSHH symbols because that is where they meet them, on a COSHH assessment sheet.
- What shape and colour are the hazard pictograms?
- A diamond with a distinctive red border and a white background, with the symbol printed in black. More than one pictogram can appear on a single product label.
- Which COSHH symbol covers wet cement?
- In practice the corrosion pictogram, because wet cement is highly alkaline and HSE warns that a serious burn or ulcer can develop rapidly where it is trapped against the skin. Cement has no harmonised classification in law, so the exact pictograms on a bag are set by the supplier. Read the label and the COSHH assessment rather than assuming.
- What is the difference between the exclamation mark and the health hazard symbols?
- Severity. The exclamation mark covers the less severe effects such as irritation, while the serious health hazard symbol covers effects such as cancer, damage to fertility, organ damage and respiratory sensitisation.
- Do I need to know all nine for the CSCS test?
- You will not be asked to name all nine in order, but you are expected to recognise what a pictogram is telling you and to act on it, which usually means checking the COSHH assessment before you start and wearing the protection it specifies.