Hazard Signs: What They Mean and How to Use Them

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Working with hazardous chemicals has always been a dangerous task. In the past, there was no standard system or labelling requirements to communicate the risks of working with hazardous materials.

As a result, employees often didn’t know what they were dealing with and used their best judgment when transporting, storing, or using hazardous chemicals. Such situations were not ideal and posed a significant risk to the safety of those working with the material.

Therefore, in an effort to keep employees safe, the United Nations (UN) developed the Globally Harmonized System of Classification and Labelling of Chemicals (GHS).

What is the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)?

GHS is an internationally-recognised standard used for communicating the hazards of chemicals in a uniform way that is understood by everyone around the world. GHS serves as a universal language, ensuring that everyone is on the same page when dealing with hazardous materials.

GHS has a set of defined hazard signs (also sometimes called warning signs or safety signs) that are used to alert workers of potential dangers.

In this article, we will take a closer look at the different GHS hazard signs and explain their meaning and how to use them.

But, before we go into GHS hazard signs, let’s first define what hazard signs are.

What Are Hazard Symbols?

Hazard symbols are pictograms used to quickly and clearly communicate the hazards associated with a chemical or substance. Each hazard symbol is assigned a specific meaning and purpose, allowing workers to recognise and act on hazardous materials they encounter quickly.

Hazard symbols are diamond shaped and contain different symbols and colours. The are two sets of pictograms included within the GHS.

  1. Physical Hazards – For container labelling and workplace hazard warnings
  2. Transportation Hazards – For the transportation of hazardous materials

GHS physical hazard signs are divided into three categories.

  • Health Hazards
  • Fire and Explosion Hazards
  • Chemical and Environmental Hazards

Each category is further divided into sub-categories depending on the type of hazard posed.

GHS transportation hazards are divided into different classes depending on the type of material being transported. These include.

  • Explosives
  • Gases
  • Flammable Liquid and Solids
  • Others

These classes are further divided into sub-classes called Divisions. Divisions specify the exact hazard posed by the material being transported.

Now that we have a basic understanding of what GHS hazard signs are, let’s take a look at each one in detail.

Hazard signs are just one element of the comprehensive GHS system. Please refer to our GHS label requirements guide for more information about GHS labelling and its requirements. 

Physical GHS Hazard Pictograms

GHS Hazard Symbols in Case of Health Hazard

GHS Pictogram
Hazard Indication
Corrosion Hazard Sign
Corrosive substances
Direct contact
Severe burns, Eye damage, Instant corrosion to metals
Strong acids or bases like sulphuric acid, nitric acid and sodium hydroxide
Skull and Crossbones
Skull and Crossbones - A Hazard Sign
Poisonous substances that cause harm if they enter the human body Acute toxicity
Direct contact, oral and inhalation
Severe eye damage, Toxic if swallowed, contacted with skin or inhaled, Danger to life if swallowed, contacted with skin or inhaled
Carbon monoxide, manganese heptoxide, chlorine and hydrogen sulphide
Exclamation Mark
Hazard Sign of Exclamation Mark
Cause harm to human health
Direct contact, oral and inhalation
Skin irritation, Eye irritation/damage, Allergic skin reactions, Respiratory tract irritation, May cause numbness, dizziness and drowsiness (narcotic effect), Organ toxicity, Harmful to the ozone layer
Products containing chemicals or biohazards like bodily fluids, blood or poisonous gases.
Health Hazard
Hazard Sign of Health Hazard
Cause severe harm that results in long-term health issues
Direct contact, oral and inhalation
Breathing difficulties and diseases like asthma, Cancer, Mutagenicity, Genetic defects, Impair fertility, Harm to the unborn child, Organ damage/failure
Toxic and radioactive chemicals like mercury, chromium, lead, arsenic and uranium.

GHS Hazard Symbols in Case of Fire and Explosion

GHS Pictogram
Exploding Bomb
Exploding Bomb - Hazard Sign
Explosives, self-reactive substances and organic peroxide that may mass explode in a fire
Azidoazide azide, TNT, Di- and Tri-nitro compounds, chromyl chloride, nitroglycerine
Hazard Sign of Flame
Flammable gases, aerosols, liquids and solids that: May catch fire when in contact with air. Have a low flash point. Produce flammable gas when it comes in direct contact with water. Catch fire with very short contact with an ignition source.
Most solvents like acetone and methanol
Flame Over Circle
A Hazard Sign of Flame Over Circle
Oxidising solids, liquids or gases that cause or intensify fire or explosion.
Most halogens like fluorine, chlorine, bromine, and iodine

GHS Hazard symbols in Case of Chemical and Environmental Hazard

GHS Pictogram
Gas Cylinder
Gas Cylinder's Hazard Sign
Gases stored under pressures that may explode if heated
Liquid nitrogen, liquid helium, liquid oxygen, butane, propane
Environment (Dead Tree and Fish)
Environment Hazard Sign
Substances that are toxic to aquatic life and aquatic environments.
Cadmium, zinc, aluminium

Transportation GHS Hazard Pictograms

Class 1 - Explosives

GHS Pictogram
Division 1.1 of Explosives
Substances and articles with mass explosion hazard
Divisions 1.2 Class of Explosives
Substances and objects that pose a projected hazard but will not cause a mass explosion
Division 1.3 of Minor Blast Hazard
Substances and items that can cause a fire with a minor blast hazard, a minor projected hazard, or both but will not cause a mass explosion
Division 1.4 of Explosives
Products classified as explosives but do not pose any significant hazards
Division 1.5 of Mass Explosion
Insensitive substances with a mass explosion risk
Division 1.6 of No hazard statement
No hazard statement

Class 2 - Gases

GHS Pictogram
Division 2.1 - Sign of Gases
Flammable gases which are at 20°C and have a standard pressure of 101.3 kPa and : Ignite when mixed with 13% (or less) by volume with air; or, Have a flammable range of at least 12% with air, irrespective of the lower flammable limit.
2.1 – Alternative Sign
Division 2.1 - Alternative Sign of Gases
Division 2.2 - Sign of Class 2 Gases
Non-flammable, non-toxic gases that are. Asphyxiant (gases that dilute or replace the oxygen present in the atmosphere); or, Oxidising (gases that provide oxygen, contributing to more combustion); or, not included in the other categories
2.2 – Alternative Sign
Division 2.2 - Alternative Sign of Class 2 Gases
Division 2.3 of Toxic Gases
Toxic gases that are. Known to be poisonous or corrosive, causing human health hazards; or, Presumed to be poisonous or corrosive because they have an LC50 value equal to or less than 5000 ml/m3 (ppm).

Class 3 and 4 - Flammable Liquids and Solids

GHS Pictogram
Class 3
Class 3 Division of Flammable Liquids and Solids
Flammable liquids with a flash point of less than 60 °C and are capable of supporting combustion
Class 3 – Alternative Sign
Class 3 - Alternative sign of Flammable Liquids and Solids
Division 4.1 of Flammable Liquids and Solids
Flammable solids, self-reactive substances and solid desensitized explosives that. Are readily combustible, Cause or contribute to fire because of friction, May undergo a strongly exothermic reaction, May explode if not diluted sufficiently.
Division 4.2 of Flammable Liquids and Solids
Substances and articles prone to spontaneous combustions under normal transportation conditions and contact with air
Division 4.3 Sign of Flammable Liquids and Solids
Substances and articles that emit flammable gases when exposed to water
4.3 – Alternative Sign
Division 4.3 - Alternative Sign of Flammable Liquids and Solids

Other Transport Classes

GHS Pictogram
Division 5.1 of Other Transport
Oxidising substances and articles that are not necessarily combustible themselves but may cause or contribute to the combustion of other materials by emitting oxygen.
Division 5.2 Sign of Other Transport
Organic peroxides that contain the bivalent –O–O– structure and are considered derivatives of hydrogen peroxide, where one or both hydrogen atom is replaced with organic radicals
5.2 – Alternative Sign
Division 5.2 Alternative Sign of Other Transport
Division 6.1 Class of Other Transport
Toxic products with. An LD50 value ≤ 300 mg/kg (oral); or, An LD50 value ≤ 1000 mg/kg (dermal); or, An LC50 value ≤ 4000 ml/m3
Division 6.2 of Infectious Substances
Infectious substances and articles very harmful to human health
Class 7
Class 7 Division of Radioactive materials
Radioactive materials
Class 8
Class 8 Division of Corrosive items
Corrosive items that. Cause complete thickness destruction of intact tissue after less than four hours of exposure; or, Show corrosion on either steel or aluminium surfaces at a rate greater than 6.25 mm per year at a temperature of 55 °C.
Class 9
Class-9 Division of Other Dangerous Substances
Other dangerous substances and articles that pose risks to humans


Hazard signs are essential tools that help identify potential dangers. They are necessary to ensure the safety of workers who may come into contact with hazardous materials.

In this blog post, we’ve taken a look at what hazard signs mean and how to use them. Remember, if you see a hazard sign, take the appropriate action and follow all safety protocols for a safe working environment.

There’s no better way to print hazard signs and GHS labels than using a thermal printer. Thermal printers provide high-quality prints, ensuring maximum visibility for your hazard signs.

At Triton, we offer a variety of thermal printers from brands such as Honeywell, Zebra, and TSC that can help you print GHS hazard symbols quickly and accurately. With our durable, long-lasting printing consumables, you’ll get the best possible results for your hazard labels.  We also offer BarTender software to help make labels that may contain hazard signs.

We also have a team of experts who are always ready to help you choose the right labelling solution for your needs. Contact us today via the live chat widget below, and let us help you find the perfect thermal printer and labels for GHS labelling.

We hope this article has been informative and helpful in providing you with an understanding of GHS symbols.

Thanks for reading!

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