Hazardous Chemical Symbols: The 9 GHS Pictograms, Table and Quiz

Today's hazardous chemical symbols are the 9 GHS pictograms (Globally Harmonized System): a black symbol inside a red-bordered diamond. The nine symbols are explosive, flammable, oxidiser, gas under pressure, corrosive, acute toxicity, exclamation mark (irritant), health hazard, and environmental hazard. They appear on product labels and in section 2 of the MSDS/SDS. A substance can carry more than one symbol.

Table of the 9 chemical symbols and their meaning

Quiz: guess the chemical symbol

Test yourself before a lab session or safety audit: pick the right name for each symbol.

Each symbol: meaning, hazard classes and handling

Symbol GHS01: Explosive

Substances that may explode or decompose violently from heat, fire, friction, or impact.

Hazard classes:

• Explosives
• Self-reactive substances, types A–B
• Organic peroxides, types A–B

General handling: Keep away from heat, flame, and friction; do not grind or heat in a closed container.

Symbol GHS02: Flammable

Substances that burn easily or release flammable gas on contact with water or air.

Hazard classes:

• Flammable gases, aerosols, liquids, and solids
• Pyrophoric and self-heating substances
• Substances that emit flammable gas in contact with water
• Self-reactive substances and organic peroxides

General handling: Keep away from flames, sparks, and hot surfaces; store in a flammables cabinet in tightly closed containers.

Example chemicals with this symbol: Acetic Acid (CH3COOH), Acetone (C3H6O), Benzene (C6H6), Ethyl Acetate (C4H8O2), Methanol (CH3OH), Naphthalene (C10H8), Sulfur (S), Toluene (C7H8), n-Hexane (C6H14)

Symbol GHS03: Oxidizer

Oxidisers: may cause or intensify fire by releasing oxygen.

Hazard classes:

• Oxidising gases
• Oxidising liquids
• Oxidising solids

General handling: Store away from flammable materials, organic substances, and reducing agents.

Example chemicals with this symbol: Hydrogen Peroxide (H2O2), Nitric Acid (HNO3), Potassium Dichromate (K2Cr2O7), Silver Nitrate (AgNO3)

Symbol GHS04: Compressed gas

Gas contained in a pressurised cylinder. May explode if heated; refrigerated gas may cause cryogenic burns.

Hazard classes:

• Compressed gases
• Liquefied gases
• Refrigerated liquefied gases
• Dissolved gases

General handling: Secure cylinders upright, keep away from heat and direct sunlight, and use a suitable regulator.

Symbol GHS05: Corrosive

Corrosives: destroy skin, eyes, or metals on contact.

Hazard classes:

• Corrosive to metals
• Skin corrosion, category 1
• Serious eye damage, category 1

General handling: Wear chemical-resistant gloves and eye or face protection; store acids and bases separately.

Example chemicals with this symbol: Acetic Acid (CH3COOH), Ammonia Solution (Ammonium Hydroxide) (NH3 / NH4OH), Calcium Chloride (CaCl2), Hydrogen Peroxide (H2O2), Nitric Acid (HNO3), Phenol (C6H5OH), Potassium Dichromate (K2Cr2O7), Potassium Hydroxide (KOH), Salicylic Acid (C7H6O3), Silver Nitrate (AgNO3)

Symbol GHS06: Acute toxicity

Acute toxicity: small amounts can cause severe poisoning or death if swallowed, in contact with skin, or inhaled.

Hazard classes:

• Acute toxicity, categories 1–3 (oral, dermal, inhalation)

General handling: Work in a fume hood, do not eat or drink in the lab, and store locked with a usage log.

Example chemicals with this symbol: Aspirin (Acetylsalicylic Acid) (C9H8O4), Barium Chloride (BaCl2), Chloroform (CHCl3), Nitric Acid (HNO3), Phenol (C6H5OH), Potassium Chromate (K2CrO4), Potassium Dichromate (K2Cr2O7), Potassium Hydroxide (KOH)

Symbol GHS07: Harmful / irritant

Exclamation mark: less severe health hazards such as irritation or harmful effects.

Hazard classes:

• Acute toxicity, category 4
• Skin and eye irritation, category 2
• Skin sensitisation
• Specific target organ toxicity, single exposure, category 3 (respiratory irritation, drowsiness/dizziness)
• Hazardous to the ozone layer

General handling: Avoid contact with skin and eyes; use in a well-ventilated area.

Example chemicals with this symbol: Acetic Acid (CH3COOH), Acetone (C3H6O), Ammonia Solution (Ammonium Hydroxide) (NH3 / NH4OH), Ammonium Chloride (NH4Cl), Benzene (C6H6), Calcium Chloride (CaCl2), Citric Acid (C6H8O7), EDTA (Ethylenediaminetetraacetic Acid) (C10H16N2O8), Ethyl Acetate (C4H8O2), Hydrogen Peroxide (H2O2)

Symbol GHS08: Health hazard

Serious or long-term health hazards, including effects that appear after repeated exposure.

Hazard classes:

• Respiratory sensitisation
• Germ cell mutagenicity
• Carcinogenicity
• Reproductive toxicity
• Specific target organ toxicity (single exposure categories 1–2 and repeated exposure)
• Aspiration hazard

General handling: Minimise exposure: use a fume hood and personal protective equipment, and follow the exposure limits in SDS section 8.

Example chemicals with this symbol: Acetic Acid (CH3COOH), Acetone (C3H6O), Ammonia Solution (Ammonium Hydroxide) (NH3 / NH4OH), Ammonium Chloride (NH4Cl), Aspirin (Acetylsalicylic Acid) (C9H8O4), Barium Chloride (BaCl2), Benzene (C6H6), Calcium Chloride (CaCl2), Chloroform (CHCl3), EDTA (Ethylenediaminetetraacetic Acid) (C10H16N2O8)

Symbol GHS09: Environmental hazard

Environmental hazard: toxic to aquatic life with long-lasting effects.

Hazard classes:

• Hazardous to the aquatic environment: acute category 1, chronic categories 1–2

General handling: Do not discharge to drains or soil; hand waste to a licensed hazardous-waste contractor.

Example chemicals with this symbol: Ammonia Solution (Ammonium Hydroxide) (NH3 / NH4OH), Ammonium Chloride (NH4Cl), Benzene (C6H6), Chloroform (CHCl3), Iodine (I2), Naphthalene (C10H8), Paracetamol (Acetaminophen) (C8H9NO2), Phenol (C6H5OH), Potassium Chromate (K2CrO4), Potassium Dichromate (K2Cr2O7)

Signal words: Danger and Warning

Next to the symbols, a GHS label carries a signal word: DANGER for more severe hazard categories and WARNING for less severe ones. Details are given by H-coded hazard statements (e.g. H314: causes severe skin burns and eye damage) and P-coded precautionary statements (e.g. P280: wear gloves and eye protection).

The old orange square symbols and their GHS equivalents

Before the GHS, many packages used black symbols on orange squares with letter codes. They have been replaced but still appear on old stock and in textbooks. The table shows the GHS pictograms that most often replace them; the exact equivalent depends on each substance's classification, so always refer to the current GHS label and SDS.

Frequently asked questions

How many hazardous chemical symbols are there?

The GHS uses 9 pictograms: explosive, flammable, oxidiser, gas under pressure, corrosive, acute toxicity, exclamation mark (irritant/harmful), health hazard, and environmental hazard.

What is the difference between the skull and the health hazard symbol?

The skull (GHS06) means acute toxicity: fast and potentially fatal effects. The health hazard symbol (GHS08) means serious or long-term effects such as cancer, mutations, or reproductive harm.

What does the exclamation mark symbol mean?

The exclamation mark (GHS07) marks less severe health hazards: skin or eye irritation, skin sensitisation, harmful if swallowed, or drowsiness and dizziness if inhaled.

Can one substance have more than one symbol?

Yes. Concentrated strong acids are often labelled corrosive and exclamation mark, and organic solvents can carry flammable, exclamation mark and health hazard together.

Where can I find a substance's hazard symbols?

On the product label and in section 2 (Hazard identification) of the MSDS/SDS. Search for the SDS of the substance you use on our MSDS page.

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This summary is for information purposes and follows the UN GHS. The classification of a specific product always follows its manufacturer's label and official SDS.