Hazard symbols explained: the COSHH and GHS pictograms

The red-bordered diamonds on a chemical label are hazard pictograms. There are nine of them, and each one stands for a different kind of danger. They are often called COSHH symbols, because they come up in COSHH assessments, but they are set by the classification and labelling rules: GB CLP, based on the UN's Globally Harmonised System (GHS). This guide goes through each symbol in turn: what it means, the hazard statements that come with it, and what it means for handling.

For the law behind them and how a COSHH assessment works, see COSHH and safety data sheets. Terms are defined in the glossary.

The nine hazard symbols at a glance

Names and meanings are from HSE. The GHS codes and hazard statement wording are from PubChem's GHS reference.

A hazard statement (an H-code) describes the nature of the hazard. The label's precautionary statements (P-codes) give the recommended measures to prevent harm (HSE). The pictogram tells you the kind of hazard at a glance. The H-codes and the safety data sheet tell you the detail.

Explosive symbol (GHS01, exploding bomb)

A bomb bursting outwards. It marks substances and mixtures that can explode, or that give a fire or projection hazard. Hazard statements in this group start with H20, such as H204, "Fire or projection hazard" (PubChem).

In practice: explosives are rare among routine lab reagents. Anything carrying this symbol needs specialist storage and handling, set out in its safety data sheet.

Flammable symbol (GHS02, flame)

A flame. It marks flammable gases, liquids and solids, and substances that catch fire on their own or give off flammable gas with water. Common examples are H225, "Highly flammable liquid and vapour", and H226, "Flammable liquid and vapour" (PubChem).

In practice: many lab solvents carry this symbol. Keep them away from heat, sparks and flames, keep containers closed, and store them in a flammable cabinet. See storing lab chemicals safely.

Oxidising symbol (GHS03, flame over circle)

A flame above a circle. An oxidiser doesn't necessarily burn itself, but it supplies oxygen that makes other materials burn more fiercely. Examples are H271, "May cause fire or explosion; strong oxidiser", and H272, "May intensify fire; oxidiser" (PubChem).

In practice: store oxidisers away from flammables and other combustible material. See oxidation and reduction for the chemistry.

Gas under pressure symbol (GHS04, gas cylinder)

A gas cylinder. It marks gases held under pressure, including refrigerated liquefied gases. Examples are H280, "Contains gas under pressure; may explode if heated", and H281, "Contains refrigerated gas; may cause cryogenic burns or injury" (PubChem).

In practice: cylinders need securing upright and keeping away from heat. Liquid nitrogen carries the refrigerated-gas warning. See liquid nitrogen and cryogenic storage.

Corrosive symbol (GHS05, corrosion)

Liquid dripping from two test tubes onto a surface and a hand, eating into both. It marks substances that cause severe skin burns and eye damage (H314), serious eye damage (H318), or that may corrode metals (H290) (PubChem).

In practice: strong acids and bases often carry this symbol. Wear goggles and suitable gloves, pour slowly, and store corrosives low down, in a cabinet with a spill tray. See lab gloves and eye protection and acids and bases.

Toxic symbol (GHS06, skull and crossbones)

A skull and crossbones. It marks substances that can be fatal or toxic after a single exposure, by mouth, through the skin or by breathing them in. Examples are H300, "Fatal if swallowed", H301, "Toxic if swallowed", H310, "Fatal in contact with skin", and H330, "Fatal if inhaled" (PubChem).

In practice: handle these in a fume cupboard where the safety data sheet says so, avoid making dust or aerosols, and keep them locked away. See fume cupboards and safety cabinets.

Exclamation mark symbol (GHS07, harmful or irritant)

An exclamation mark. HSE describes it as "health hazard/hazardous to the ozone layer" (HSE). It covers less severe effects than the skull and crossbones or the health hazard symbol. Examples are:

• H302, "Harmful if swallowed"
• H315, "Causes skin irritation"
• H317, "May cause an allergic skin reaction"
• H319, "Causes serious eye irritation"
• H335, "May cause respiratory irritation"
• H336, "May cause drowsiness or dizziness"
• H420, "Harms public health and the environment by destroying ozone in the upper atmosphere"

(PubChem)

In practice: this is the symbol most often seen on routine reagents. Gloves, eye protection and good ventilation usually manage the risk, as the safety data sheet's section 8 sets out.

Health hazard symbol (GHS08)

The outline of a person with a starburst on the chest. It marks serious health hazards, often from longer or repeated exposure. Examples are:

• H334, "May cause allergy or asthma symptoms or breathing difficulties if inhaled"
• H340, "May cause genetic defects"
• H350, "May cause cancer"
• H360, "May damage fertility or the unborn child"
• H372, "Causes damage to organs through prolonged or repeated exposure"

(PubChem)

In practice: these effects may not show for a long time, so control exposure every time, not only when something seems wrong. A COSHH assessment should cover substances with this symbol in detail.

Environment symbol (GHS09, dead tree and fish)

A dead tree and a dead fish. It marks substances that are toxic to aquatic life: H400, "Very toxic to aquatic life", and H410, "Very toxic to aquatic life with long-lasting effects" (PubChem).

In practice: never pour these down the sink. Collect them as chemical waste and follow section 13 of the safety data sheet.

Signal words: Danger and Warning

Next to the pictograms, a label carries one signal word. "Danger" is used for the more serious hazards and "Warning" for the less serious ones (HSE).

The old orange hazard symbols

Before CLP, chemicals in Great Britain were labelled under the CHIP regulations. CHIP used black symbols on an orange-yellow background (HSE, HSG71). CLP replaced CHIP on 1 June 2015. The new pictograms look similar to the old symbols, but have a new shape, design and colour (HSE). Older bottles in a store may still carry the orange symbols. If so, check that a current safety data sheet is on file.

Hazard pictograms and transport diamonds

The diamonds on a delivery box are not the same as the pictograms on a bottle. Transport labels use coloured diamonds and come with a UN number, a four-digit code for the substance. They are set by the rules for carrying dangerous goods, not by CLP. See transport labels and UN numbers in the COSHH guide. Section 14 of a safety data sheet gives the transport details.

Related guides

For the law, the COSHH assessment and the 16 sections of a safety data sheet, see COSHH and safety data sheets. For cabinets and spill kits, see storing lab chemicals safely. For choosing protection, see lab gloves and eye protection. This guide gives general information and doesn't replace a product's own label and safety data sheet. Each product page has a safety data sheet link, or says the sheet is available on request.