Hazardous Chemical Symbols: The 9 GHS Pictograms Explained

Today's hazardous chemical symbols are the 9 GHS pictograms (Globally Harmonized System): a black symbol inside a red-bordered diamond. They appear on product labels and in section 2 of the MSDS/SDS. A substance can carry more than one symbol. Below is the meaning of each symbol, the hazard classes it covers, how to handle it, and example chemicals with their MSDS pages.

GHS01 – Explosive
Explosive
GHS02 – Flammable
Flammable
GHS03 – Oxidizer
Oxidizer
GHS04 – Compressed gas
Compressed gas
GHS05 – Corrosive
Corrosive
GHS06 – Acute toxicity
Acute toxicity
GHS07 – Harmful / irritant
Harmful / irritant
GHS08 – Health hazard
Health hazard
GHS09 – Environmental hazard
Environmental hazard

Symbol GHS01: Explosive

GHS01 – ExplosiveSubstances 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

GHS02 – FlammableSubstances 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

GHS03 – OxidizerOxidisers: 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

GHS04 – Compressed gasGas 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

GHS05 – CorrosiveCorrosives: 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

GHS06 – Acute toxicityAcute 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

GHS07 – Harmful / irritantExclamation 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

GHS08 – Health hazardSerious 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

GHS09 – Environmental hazardEnvironmental 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

Before the GHS, many packages used black symbols on orange squares with letter codes such as T (toxic), C (corrosive), F (flammable), O (oxidising), Xn (harmful), Xi (irritant), N (dangerous for the environment), and E (explosive). These have been replaced by GHS pictograms but may still be seen on old stock or in textbooks. 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.

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.

Find a chemical MSDS / SDS Ask via WhatsApp

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.