Construction safety signs: colours and shapes explained (UK)

You do not need to memorise hundreds of safety signs. Workplace safety signs in Great Britain follow one simple system of colours and shapes. Learn the system once, and you can understand a sign you have never seen before — on site, and in the CSCS test. This guide explains the five main types of sign, the hazard stripes you see on site, and the law behind them.

Where the rules come from

Safety signs at work in Great Britain are covered by the Health and Safety (Safety Signs and Signals) Regulations 1996. The Health and Safety Executive (HSE) publishes guidance on them, called L64. Northern Ireland has its own, equivalent regulations from the same year.

The design of the pictures — the little symbols inside the signs — is covered by a standard called BS EN ISO 7010. HSE's guidance says you can use signs from BS EN ISO 7010 to comply with the Regulations, and that small variations in pictures are fine as long as the sign keeps its intrinsic features: its shape and its colours.

That is good news for you. The shape and colour are fixed. The picture can change a little. So if you learn the shapes and colours, you will always know what kind of message a sign is giving.

The system in one table

The quick way to remember it:

• Red = stop, don't, or fire equipment
• Yellow = watch out
• Blue = do this
• Green = safe, this way out, first aid

Prohibition signs: "Do not"

Shape: round. Colours: black picture on a white background, with a red edge and a red diagonal line across it. HSE's guidance says the red part should be at least 35% of the sign.

A prohibition sign tells you that something is forbidden because it could cause or increase danger.

Examples in HSE's guidance include:

• No smoking
• Smoking and naked flames forbidden
• No access for unauthorised persons
• No access for pedestrians
• No access for industrial vehicles
• Not drinkable
• Do not touch
• Do not extinguish with water

Tip: the red line across the picture always means "no". If you see a red circle with a line through it, whatever is in the picture is not allowed.

Warning signs: "Be careful"

Shape: triangle. Colours: black picture on a yellow background, with a black edge. The yellow part should be at least 50% of the sign.

A warning sign tells you there is a hazard nearby. It does not tell you what to do. It tells you what could hurt you, so you can take care.

Examples in HSE's guidance include:

• Flammable material or high temperature
• Explosive material
• Toxic material
• Corrosive material
• Overhead load
• Industrial vehicles
• Danger: electricity
• Obstacles
• Drop
• General danger

Tip: in the HSE's colour table, yellow means "be careful, take precautions" and "examine".

Mandatory signs: "You must"

Shape: round. Colours: white picture on a blue background. The blue part should be at least 50% of the sign.

A mandatory sign tells you to do something. On a construction site, most of them are about personal protective equipment (PPE).

Examples in HSE's guidance include:

• Safety helmet must be worn
• Eye protection must be worn
• Ear protection must be worn
• Safety boots must be worn
• Safety gloves must be worn
• Respiratory equipment must be worn
• Safety harness must be worn
• Face protection must be worn
• Pedestrians must use this route

Tip: don't mix up prohibition and mandatory signs. Both are round. Red with a line means don't. Solid blue means do.

HSE's guidance also says that any text added under a mandatory sign should use the word "must" — not "should" or "may". A blue sign is an instruction, not a suggestion.

Emergency escape and first-aid signs: "Safe condition"

Shape: square or rectangle. Colours: white picture on a green background. The green part should be at least 50% of the sign.

These are often called safe condition signs. They show you the way to safety, or where to find first aid.

Examples include:

• Emergency exit and escape route signs, often with a running figure and an arrow
• First aid
• Stretcher
• Eyewash
• Safety shower
• Emergency telephone for first aid or escape

In the HSE colour table, green means emergency escape and first aid — doors, exit routes, equipment and facilities — and also "no danger" and "return to normal".

Fire-fighting equipment signs: "The fire equipment is here"

Shape: square or rectangle. Colours: white picture on a red background. The red part should be at least 50% of the sign.

These signs show where to find fire-fighting equipment.

Examples include:

• Fire hose
• Fire extinguisher
• Ladder
• Fire alarm
• Emergency fire telephone

Tip: red appears in two kinds of sign. A red circle with a line is a prohibition. A red square or rectangle points to fire-fighting equipment. The shape tells you which.

Hazard stripes on site

You will also see stripes on barriers, edges and obstacles. Under the Regulations, places where there is a risk of:

• walking into an obstacle,
• falling, or
• objects falling

can be marked with alternating yellow and black stripes, or red and white stripes. The stripes should be at about 45 degrees and roughly the same size.

For vehicle routes inside a workplace, the Regulations say that where it is necessary to protect workers, routes must be clearly marked with continuous stripes in a clearly visible colour, preferably white or yellow.

Stripes are a warning, not a barrier. HSE's guidance points out that in many cases proper fall protection, such as secure barriers, is still needed.

Signs are the last line, not the first

This is an important idea for both the site and the test. HSE's guidance says safety signs are not a substitute for other ways of controlling risk. Employers should first remove or control a risk in other ways — for example, with engineering controls or a safe system of work. A sign is used to warn about the risk that is left, or to tell people what they need to do about it.

So a "Hard hats must be worn" sign does not make a site safe on its own. It reminds you of one control that is part of a bigger plan.

HSE's guidance also says employers should make sure workers understand the signs they see, with training where needed. New and young workers, especially, may not know the less common signs. If you see a sign you do not understand, ask.

A quick self-test

Cover the answers and try these. They test the system, not memory.

1. A round sign with a blue background and a white picture of ear defenders. (Mandatory — you must wear ear protection.)
2. A yellow triangle with a black picture of a forklift. (Warning — industrial vehicles in the area.)
3. A green rectangle with a running figure and an arrow. (Safe condition — emergency exit this way.)
4. A red rectangle with a white picture of an extinguisher. (Fire-fighting equipment — extinguisher here.)
5. A white circle with a red edge, a red diagonal line and a picture of a cigarette. (Prohibition — no smoking.)

If you got all five, you already know the system. That is most of what you need.

The short version

• Circle with red line — don't. Blue circle — do. Yellow triangle — careful. Green square — safe way or first aid. Red square — fire equipment.
• Shape and colour are fixed; the picture can vary slightly.
• Yellow/black or red/white stripes mark obstacles, drops and falling-object areas.
• Signs support other safety measures. They never replace them.

Signs are one part of the test. For the full picture, read what's in the CSCS test and follow the two-week revision plan.