The Two Hazard Groups And How They Get Into Your Body

There are two types of hazards: physical hazards and health hazards. Physical hazards will result in immediate injury to the body. The effects of health hazards may be felt within moments or over a prolonged period from initial exposure and are primarily concerned with illness or disease.

There are four ways hazardous materials can enter the body:

• Ingestion: Inadvertently swallowing hazardous materials.
• Absorption: Occurs when hazardous material enters the body through the skin or an open wound.
• Inhalation: Breathing in hazardous fumes.
• Injection: Occurs when a needle containing hazardous material pierces the skin.

Understanding WHMIS Hazard Groups, Classes & Categories for Workplace Safety

Workplace safety is a top priority in Canada, and understanding Workplace Hazardous Materials Information Systems is essential for handling hazardous materials safely. By learning these classifications, workers can better identify risks and take appropriate precautions.

What Are WHMIS Hazard Classes?

Hazard classes group products with similar hazardous properties. Most classes align with GHS standards, but some are specific to WHMIS.

Physical Hazard Classes

Hazard Class	Key Risks
Flammable gases, liquids, solids	Fire or explosion hazards
Oxidizing gases, liquids, solids	Intensify fires or cause explosions
Gases under pressure	Explosion risk if heated; cryogenic burns
Self-reactive substances	May ignite or explode spontaneously
Pyrophoric liquids/solids	Ignite instantly when exposed to air
Corrosive to metals	Can chemically damage metals
Combustible dusts	Fire or explosion risk when airborne
Organic peroxides	Fire or explosion risk if heated

Health Hazard Classes

Hazard Class	Key Risks
Acute toxicity	Fatal, toxic, or harmful if inhaled/swallowed
Skin corrosion/irritation	Severe burns or reversible damage
Respiratory sensitization	May cause asthma or allergic reactions
Carcinogenicity	May cause cancer
Reproductive toxicity	Harms fertility or unborn children
Biohazardous materials	Infectious microorganisms causing disease

Note: WHMIS does not currently include the Explosives hazard class, as it’s regulated under other Canadian laws.

What Are WHMIS Hazard Categories?

Each hazard class is further divided into categories, ranked by severity:

• Category 1 = Most hazardous
• Category 2, 3, etc. = Decreasing hazard level

For example:

• Flammable liquids (Category 1) are more dangerous than Flammable liquids (Category 3).
• Carcinogenicity (Category 1A) poses a higher cancer risk than Carcinogenicity (Category 1B).
• Some exceptions exist (e.g., Gases under pressure categories describe physical state, not hazard level).

How to Identify Hazard Classes & Categories

All hazardous products must have:

• Labels with hazard pictograms
• Safety Data Sheets (SDS) with hazard details

By reviewing these, workers can:

• Recognize hazards
• Follow proper handling procedures
• Prevent accidents