GHS Course page 2 | Industrial & Construction Safety Solutions



Hazard Classifications

Based on properties, hazardous products are assigned to hazard classes such as Corrosive to Metals or Serious Eye Damage/Eye Irritation. The Hazard Class and Category are a guide to the type of hazard, degree of hazard and precautions to follow. Some products present more than one hazard, and therefore belong to more than one hazard class.


Most Hazard classes and categories are assigned a symbol reflecting the type or severity of the hazard. The symbol is called a pictogram when it is framed by a red square set on point, the exception is the biohazard pictogram which is in a round black border. Each pictogram is an image that will help to immediately illustrate what type of hazard is present.


WHMIS Pictogram


What do the Pictograms Mean?


WHMIS Pictogram Meaning


Many of these pictograms may look familiar, some are based on the placards and labels used when transporting goods. The two new pictograms are the exclamation mark and the health hazard, you may also see the environment pictogram is a supplier has chosen to use it.

Hazard Groups

There are two hazard groups: Physical and Health, and each group is made up of a number of classes and categories.

Physical Hazards


Physical Hazards Photo


Flammable Gases

Flammable Aerosols

Oxidizing Gases

Flammable Solids

Self-Reactive Substances & Mixtures

Pyrophoric Liquids

Substances & Mixtures which, in contact with water, emit flammable gases

Oxidizing Liquids

Oxidizing Peroxides

Simple Asphyxiants

Pyrophoric Gases

Physical Hazards not otherwise Classified

Gases Under Pressure

Flammable Liquids

Combustible Dusts

Pyrophoric Solids

Self-Heating Substances & Mixtures

Corrosive to Metals


Health Hazards


Health Hazards Photo


Acute Toxicity

Skin Corrosion/Irritation

Serious Eye Damage/Eye Irritation

Respiratory or Skin Sensitization

Germ Cell Mutagenicity


Reproductive Toxicity

Specific Target Organ Toxicity – Single Exposure

Specific Target Organ Toxicity – Repeated Exposure

Aspiration Hazard

Biohazardous Infectious Materials

Health Hazards not otherwise classified



Hazard classes consist of categories or subcategories, the category identifies the degree of the hazard. Category 1 is always more hazardous than Category 2 or 3; similarly, Subcategory 1A is always more hazardous than subcategory 1B or 1C.


Flammable liquids is a hazard class. Within this class, there are 4 divisions or categories, each with different flash point and/or initial boiling point cut-off values:

  • Category 1: Flash point <23°C and initial boiling point <35°C (most flammable)

  • Category 2: Flash point <23°C and initial boiling point >35°C

  • Category 3: Flash point >23°C and <60°C

  • Category 4: Flash point >60°C and <93°C


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