Hazard Symbols: UK Signs, Pictograms and Colours
Hazard symbols explained: the 9 GB CLP chemical pictograms, safety sign colours and shapes, and how both fit your RAMS on UK sites and in buildings you run.
A cleaner on a night shift picks up an unlabelled spray bottle from the cupboard under a sink. A labourer decants a solvent into a water bottle "just for the day". A new starter walks past a yellow triangle on a plant room door without a second look. None of them set out to take a risk. They just didn't read, or didn't have, the hazard symbols that were meant to warn them.
Hazard symbols are the standard pictures used in the UK to warn people about danger at work. There are two families. The first is the nine red-bordered diamond pictograms on chemical labels, set by the GB CLP Regulation (the GB version of the global GHS system). The second is workplace safety signs, which follow the Health and Safety (Safety Signs and Signals) Regulations 1996: red circles for things you mustn't do, yellow triangles for warnings, blue circles for things you must do, and green or red rectangles for escape routes, first aid and fire-fighting equipment.
This guide covers both, with the site and building examples you'll actually meet. If you need the detail on COSHH assessments themselves, our COSHH regulations guide goes deeper on that side.
What are hazard symbols?
A hazard symbol is a picture that tells you something about a danger without needing words. That matters on a site where people speak different first languages, where lighting is poor, or where someone's in a hurry.
In the UK you'll come across two sets, and it's worth keeping them separate in your head because different law governs each one:
- Chemical hazard pictograms: the red and white diamonds printed on the label of a product by whoever supplies it. They describe what the substance inside can do to you or the environment.
- Safety signs: the circles, triangles and rectangles fixed to walls, doors, hoarding and equipment by the employer. They tell people what to do, what not to do, and where to go.
Both are there to back up your risk controls, not replace them. A sign on a door doesn't make the room safe. It tells people about a risk that's left after everything else has been done. That's a useful way to think about the difference between a hazard and a risk: the symbol points at the hazard, your controls deal with the risk.
The 9 GHS/CLP hazard symbols explained
Chemical labels in Great Britain follow the GB CLP Regulation (Classification, Labelling and Packaging). According to the HSE's page on hazard pictograms, they appear as a diamond with a red border and a white background, with a black symbol inside. A single product can carry more than one. Each pictogram also has a code from the UN's Globally Harmonised System, running from GHS01 to GHS09.
1. Explosive (GHS01): exploding bomb
Used for explosives, self-reactive substances and some organic peroxides. It's rare on a general building site.
2. Flammable (GHS02): flame
Flammable gases, liquids, aerosols and solids. On site this means petrol for disc cutters and generators, spray paint, expanding foam, solvent-based adhesives and some cleaners. It's the one that should make you think about hot works, storage away from ignition sources and having the right fire extinguisher type nearby.
3. Oxidising (GHS03): flame over circle
Oxidisers don't necessarily burn themselves, but they feed a fire with oxygen and can make it far worse. Examples include some pool and water treatment chemicals and the oxygen used in gas cutting. Keep them away from flammables, oils and grease.
4. Gas under pressure (GHS04): gas cylinder
Any gas stored under pressure, including compressed, liquefied and dissolved gases. Think LPG for heaters and roofing torches, oxy-acetylene sets and nitrogen used by HVAC and refrigeration engineers. The hazard is the pressure itself (a damaged cylinder can become a projectile) and, for some gases, very cold liquid that causes burns.
5. Corrosive (GHS05): liquid eating into a hand and a surface
Substances that can burn skin, cause serious eye damage or corrode metal. Drain cleaners, descalers, some brick and patio cleaners and many concentrated cleaning chemicals carry it. HSE explains that some cleaning products now carry the corrosive diamond because they can cause serious eye damage, even though the product itself is no more hazardous than it was under the old rules.
6. Acute toxicity (GHS06): skull and crossbones
Substances that can kill or cause serious harm in small amounts, whether swallowed, breathed in or absorbed through the skin. Some pest control products carry it. Anything with this pictogram needs secure storage, a proper assessment and a clear plan for spills and first aid.
7. Health hazard (GHS07): exclamation mark
The broadest and least severe of the health pictograms. It covers irritants, skin sensitisers, harmful substances and effects such as drowsiness. HSE lists it for ozone layer hazards too. Many everyday site and FM products carry it, which is exactly why people start ignoring it. Don't.
8. Serious health hazard (GHS08): silhouette with a starburst on the chest
This one covers the long-term damage: substances that can cause cancer, damage fertility, change genetic material, sensitise the lungs (asthma) or damage organs through repeated exposure. It also covers aspiration hazards, where a liquid that gets into the lungs can be fatal. Isocyanate-based paints and foams, some resins and diesel commonly carry it. Because the harm can take years to show, this pictogram deserves more attention than it usually gets.
9. Hazardous to the environment (GHS09): dead tree and fish
Substances that are toxic to aquatic life. Diesel, some wood preservatives and some biocides carry it. The practical point is spill control: drip trays, spill kits, and keeping it away from drains and watercourses.
Signal words, hazard statements and the old orange symbols
The pictogram is only one part of a CLP label. Read the rest too:
- Signal word: either "Danger" for the more severe hazards or "Warning" for less severe ones, as set out in HSE's guidance on signal words and statements.
- Hazard statements (H-codes, such as H318 "Causes serious eye damage") describe the nature of the hazard.
- Precautionary statements (P-codes) say how to minimise or prevent harm, for example wearing eye protection or avoiding breathing vapour.
If you still find products with the old square orange and black symbols, they date from the earlier CHIP rules, which CLP replaced on 1 June 2015. Treat anything with the old symbols as old stock, get the current safety data sheet from the supplier, and check whether it should still be on site at all.
Safety sign colours and shapes: what each one means
Workplace safety signs are covered by the Health and Safety (Safety Signs and Signals) Regulations 1996. Regulation 4 says an employer must provide and maintain suitable signs where the risk assessment shows a risk can't be avoided or adequately reduced by other means. Signs are a last layer, not a first one. Schedule 1 sets the colours and shapes, so a sign means the same thing wherever it's used.
Prohibition signs (red circle with a diagonal bar)
A round sign with a black pictogram on a white background, a red border and a red diagonal line. It tells people what they must not do. Common examples: no smoking, no unauthorised access, no pedestrians in a plant area, and no naked flames near fuel stores.
Warning signs (yellow triangle)
A triangle with a black pictogram on a yellow background and a black border. It warns of a hazard: electricity, overhead loads, forklift trucks, slippery floors, deep excavations, hot surfaces. The yellow triangle is the one most likely to become wallpaper if you put up too many of them.
Mandatory signs (blue circle)
A round sign with a white pictogram on a blue background. It tells people what they must do: wear a hard hat, wear hearing protection, wear eye protection, use the pedestrian route, keep the fire door shut. These are the signs that tie directly to your PPE rules, which our guide to the PPE at Work Regulations covers.
Safe condition signs (green rectangle or square)
A white pictogram on a green background. These show fire exits, escape routes, first aid points, eyewash stations and assembly points.
Fire-fighting equipment signs (red rectangle or square)
A white pictogram on a red background. They mark the location of extinguishers, fire hose reels, fire alarm call points and fire blankets.
Hazard marking tape and stripes
Schedule 1 also covers marking obstacles and dangerous locations with alternating yellow and black, or red and white, stripes at about 45 degrees. On site you'll see this on low beams, the edges of loading bays, barriers around openings and the corners of plant. Traffic routes may also need marking so vehicle and pedestrian routes are clear.
The regulations cover hand signals and verbal communication too, which matters for crane and plant work. A signaller needs to use signals everyone on the lift understands.
Hazard symbols on real UK sites: practical examples
Construction: groundworks and fit-out
A groundworks crew is using a petrol disc cutter, a diesel generator and a bagged cement product. That's the flammable diamond on the petrol, several diamonds on the diesel (typically flammable, health hazard, serious health hazard and environment), and often the corrosive and exclamation mark diamonds on the cement bag. The site signage adds a yellow "deep excavation" triangle, blue "hard hat" and "hi-vis" circles, and a red "no unauthorised access" circle on the gate. Your construction RAMS should pick up the substances, and the COSHH assessment should cover the cement and fuel in detail.
Facilities management: plant rooms and cleaning cupboards
An FM supervisor walking a building will see yellow electrical warning triangles on switch rooms, oxidiser and corrosive diamonds on water treatment chemicals in a plant room, and corrosive diamonds on the cleaning trolley. The common failures here aren't missing signs. They're decanted chemicals in unlabelled bottles, and cupboards where incompatible products (like a bleach-based cleaner and an acid descaler) sit side by side. For contract cleaners, our RAMS for cleaning contractors page covers the usual chemical tasks, and our facilities management risk assessment guide covers the wider picture.
Security: patrols and out-of-hours access
Security officers on mobile patrol often enter plant rooms, roof areas and construction sites alone and at night. They need to recognise a yellow triangle for an electrical or biological hazard, respect a red prohibition sign on a restricted area, and know where the nearest green first aid sign and red fire alarm call point are. It's worth adding sign recognition to the site-specific briefing for every patrol route.
Common mistakes with hazard symbols and signs
- Too many signs. A door with nine signs on it tells people nothing. Put up the signs your risk assessment calls for and take down the rest.
- Faded, damaged or out-of-date signs. Regulation 4 requires signs to be maintained, not just fixed once. Walk your site with fresh eyes.
- Decanting without relabelling. The moment a chemical goes into a spray bottle or unmarked container, the label that carried the hazard symbols is gone. Use properly labelled secondary containers.
- No training. A sign only works if people know what it means. Cover the colours and shapes at induction and in a short toolbox talk.
- Treating a sign as the control. A "wet floor" sign doesn't stop a slip if the leak is left running. Deal with the hazard first.
Where hazard symbols fit in your RAMS
Hazard symbols belong in your paperwork as well as on the wall. A good RAMS will:
- List the hazardous substances used in the task, with their pictograms and signal words taken from the product label and safety data sheet.
- Link each one to its COSHH risk assessment, with storage, PPE, spill and first aid arrangements.
- Record the safety signs needed for the task, such as warning signs around an exclusion zone or mandatory PPE signs at a work area entrance.
- Include hazard and sign recognition in the site briefing or induction.
How swiftRMS helps
swiftRMS drafts RAMS for construction, security and FM teams. You describe the task, and it produces a draft risk assessment and method statement that picks up the substances and signs you mention and cites the relevant legislation, such as COSHH, GB CLP and the Safety Signs and Signals Regulations where they apply. Our COSHH solution is built around the COSHH Regulations 2002 for the chemical side.
The draft is a starting point. You still check the actual product labels and safety data sheets, add what's specific to your site, and a competent person reviews, edits and approves the document before anyone works to it. That's what the Management of Health and Safety at Work Regulations 1999 expect, and it's how the tool is designed to be used. You can see what the output looks like on our RAMS examples page.
If you'd like to see a draft for your own task, you can generate a free RAMS preview with no signup at app.swiftrms.co.uk/try. If it's useful, there's a 14-day free trial with no card needed.
Frequently Asked Questions
How many hazard symbols are there in the UK?
There are nine chemical hazard pictograms under the GB CLP Regulation: explosive, flammable, oxidising, gas under pressure, corrosive, acute toxicity, health hazard (exclamation mark), serious health hazard and hazardous to the environment. Separately, workplace safety signs come in five main types under the Safety Signs and Signals Regulations 1996: prohibition, warning, mandatory, safe condition and fire-fighting equipment.
What do the colours of safety signs mean?
Red means prohibition, danger alarms or fire-fighting equipment. Yellow or amber means warning. Blue means a mandatory action, such as wearing PPE. Green means a safe condition, such as an escape route or first aid. The shape matters too: circles for prohibition and mandatory signs, triangles for warnings, and rectangles or squares for safe condition and fire equipment signs.
Are the old orange hazard symbols still valid?
No. The orange square symbols came from the old CHIP rules, which CLP replaced on 1 June 2015. If you find products with orange symbols, treat them as old stock. Ask the supplier for the current safety data sheet and check whether the product should still be on site.
What's the difference between a hazard symbol and a safety sign?
A chemical hazard symbol (pictogram) is printed on a product label by the supplier and tells you what the substance can do. A safety sign is put up by the employer at the workplace and tells people what to do, what not to do, or where to find escape routes and equipment. Different law covers each one: GB CLP for labels, and the Safety Signs and Signals Regulations 1996 for signs.
Do I need a sign for every hazard on site?
No. Regulation 4 of the Safety Signs and Signals Regulations requires signs where your risk assessment shows a risk remains that can't be avoided or adequately reduced by other means. Signs are the last layer, not a substitute for dealing with the hazard. Too many signs can make people ignore all of them.
Where can I learn more about COSHH hazard symbols?
Our COSHH regulations guide covers how the pictograms feed into a COSHH assessment, including safety data sheets, exposure limits and health surveillance.
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