// WHMIS/GHS/SDS

WHMIS - Hazard Classes and Categories

Important Information Canada has aligned the Workplace Hazardous Materials Information System (WHMIS) with the Globally Harmonized System of Classification and Labelling of Chemicals (GHS).

Important Information

Canada has aligned the Workplace Hazardous Materials Information System (WHMIS) with the Globally Harmonized System of Classification and Labelling of Chemicals (GHS). This document discusses the WHMIS supplier requirements as regulated by federal legislation – the Hazardous Products Act and the Hazardous Products Regulations (HPR). This document reflects the Hazardous Products Regulations requirements as of December 15, 2022. Health Canada is the government body responsible for the overall WHMIS supplier-related laws. Note that WHMIS is also regulated in the workplace by the provinces, territories and federal governments (for federally regulated workplaces) under their occupational health and safety legislation. While these jurisdictions based their WHMIS regulations on a common model, small variations between jurisdictions may exist. Suppliers and employers must use and follow the WHMIS requirements for labels and safety data sheets (SDSs) for hazardous products sold, distributed, or imported into Canada. Please refer to the following OSH Answers documents for information about WHMIS:

context WHMIS – General
context WHMIS – Pictograms
context WHMIS – Labels
context WHMIS – Safety Data Sheets (SDSs)
context WHMIS – Education and Training
context WHMIS – WHMIS Program
context WHMIS – Glossary
context WHMIS – Confidential Business Information (CBI)
context WHMIS – Variances
context WHMIS – Laboratories
context WHMIS - Information for Suppliers and Importers
context WHMIS - Legislation

How does WHMIS classification work?

context Suppliers must determine if their products meet the various physical and health properties that are regulated by the Hazardous Products Act and regulations. The specific criteria is listed in the Hazardous Products Regulations. If the product meets any of the criteria for a hazard class, it is considered to be a WHMIS hazardous product.
context The official definition of a “hazardous product” is "any product, mixture, material or substance that is classified in accordance with the regulations made under subsection 15(1) in a category or subcategory of a hazard class listed in Schedule 2; (produit dangereux)."
context All hazardous products must be labelled according to the Hazardous Products Regulations and must have a corresponding safety data sheet provided to the purchaser at the time of sale.
context Employers who produce hazardous products for use in their own workplaces have the duty to assess the hazards, classify the hazards of the products, and provide appropriate labels and safety data sheets to their workers.
context Tools to help with classification, such as the Technical Decision Trees and guidance for classification, are available from whmis.org and Health Canada.
context Please see the OSH Answers on “WHMIS – Labels” and “WHMIS – Safety Data Sheets (SDSs) for more information.

What is a hazard group?

WHMIS applies to two major groups of hazards: physical and health. Each hazard group includes hazard classes that have specific hazardous properties. The Globally Harmonized System of Classification and Labelling of Chemicals (GHS) also defines an Environmental hazards group. This group (and its classes) was not adopted in WHMIS. However, you may see the environmental classes listed on labels and Safety Data Sheets (SDSs). Including information about environmental hazards is allowed by WHMIS.

chemical Physical hazards group: based on the product's physical or chemical properties, such as flammability, reactivity, or corrosivity to metals.
general Health hazards group: based on the ability of the product to cause a health effect, such as eye irritation, respiratory sensitization (may cause allergy or asthma symptoms or breathing difficulties if inhaled), or carcinogenicity (may cause cancer).

What is a hazard class?

Hazard classes are a way of grouping together products that have similar properties. Most of the hazard classes are common to GHS and will be used worldwide by all countries that have adopted GHS. Some hazard classes are specific to WHMIS.

List of Hazard Classes

Physical Hazard Classes Health Hazard Classes Note: GHS also defines an Explosive class and the Environmental Hazards group (not mandatory). The WHMIS regulations do not currently include the Explosives hazard class. Explosives are covered by other legislation in Canada.

chemical Flammable gases (including pyrophoric gases and chemically unstable gases)
general Aerosols
chemical Oxidizing gases
chemical Gases under pressure
safety Flammable liquids
safety Flammable solids
general Self-reactive substances and mixtures
general Pyrophoric liquids
general Pyrophoric solids
general Self-heating substances and mixtures
chemical Substances and mixtures which, in contact with water, emit flammable gases
general Oxidizing liquids
general Oxidizing solids
general Organic peroxides
general Corrosive to metals
chemical Combustible dusts
general Simple asphyxiants
general Physical hazards not otherwise classified
chemical Chemicals under pressure
chemical Acute toxicity
general Skin corrosion/irritation
general Serious eye damage/eye irritation
general Respiratory or skin sensitization
general Germ cell mutagenicity
general Carcinogenicity
chemical Reproductive toxicity
chemical Specific target organ toxicity – single exposure
chemical Specific target organ toxicity – repeated exposure
general Aspiration hazard
biological Biohazardous infectious materials
general Health hazards not otherwise classified

What is a hazard category?

Each hazard class contains at least one category. The hazard categories are assigned a number (e.g., 1, 2, etc.). Categories may also be called "types". Types are assigned an alphabetical letter (e.g., A, B, etc.). In a few cases, sub-categories are also specified. Subcategories are identified with a number and a letter (e.g., 1A and 1B). Some hazard classes have only one category (e.g., corrosive to metals). Others may have two categories (e.g., carcinogenicity (cancer)) or three categories (e.g., oxidizing liquids). There are a few hazard classes with five or more categories (e.g., organic peroxides). The category tells you about how hazardous the product is (that is, the severity of the hazard). There are a few exceptions to this rule. For example, for the Gases under pressure hazard class, the hazard categories are "Compressed gas", "Liquefied gas", "Refrigerated liquefied gas" and "Dissolved gas". These classes relate to the physical state of the gas when packaged and do not describe the degree of hazard. In addition, the Reproductive Toxicity hazard class has a separate category called "Effects on or via lactation". "Effects on or via lactation" was not assigned a specific numbered category. Reproductive toxicity also has Categories 1 and 2, which relate to effects on fertility or on the unborn child. Effects on or via lactation are considered a different but related hazard within the Reproductive toxicity class.

general Category 1 is always the greatest level of hazard (that is, it is the most hazardous within that class). If Category 1 is further divided, Category 1A within the same hazard class is a greater hazard than category 1B.
general Category 2 within the same hazard class is more hazardous than category 3, and so on.

What classifications are new for the amended WHMIS?

The key changes in the December 2022 amendments of the Hazardous Products Regulations include:

context Adoption of a new physical hazard class: Chemicals Under Pressure
context A change in the name of the physical hazard class “Flammable Aerosols” to “Aerosols”
context A new hazard category for non-flammable aerosols (Aerosols – Category 3)
context A split in the hazard category Flammable Gases – Category 1 into Categories 1A and 1B
context Inclusion of Pyrophoric gases under Flammable gases – Category 1A instead of being its own hazard class.
context Inclusion of Chemically Unstable Gases into the new Flammable gases – Category 1A
context Mixtures that are classified in one of the health hazard classes that include both categories and subcategories may be classified in an applicable subcategory when there is sufficient data available to do so.
context The classification criteria for water-activated toxicants have changed to be based on the acute inhalation toxicity of the substance or mixture as sold or imported.
context The classification criteria for Reproductive Toxicity – Category 2 has been corrected to specify that adverse effects observed in humans or animals must not be considered as a secondary non-specific consequence of other toxic effects.

What are the main concerns for each physical hazard class?

These four classes cover products that can ignite (catch fire) easily. The main hazards are fire or explosion. Note: These products can catch fire very quickly (spontaneously) if exposed to air. Note: Pyrophoric gases are now included in the hazard category Flammable gases – Category 1A

chemical Flammable gases Aerosols Flammable liquids Flammable solids — General Description: The hazard class under Flammable gases – Category 1A includes Pyrophoric gases and Chemically Unstable Gases.
chemical Flammable gases Aerosols Flammable liquids Flammable solids — General Description: The hazard class Aerosols also includes a category for non-flammable aerosols (for products that may be a hazard if they burst when heated).

What are the main concerns for each health hazard class?

chemical Acute toxicity | Products classified in this hazard class are fatal, toxic or harmful if inhaled, following skin contact, or if swallowed. Acute toxicity refers to effects occurring following skin contact or ingestion exposure to a single dose, or multiple doses given within 24 hours, or an inhalation exposure of 4 hours. Acute toxicity could result from exposure to the product itself, or to a product that, upon contact with water, releases a gaseous substance that is able to cause acute toxicity.
biological Skin corrosion / irritation | This class covers products that cause severe skin burns (i.e., corrosion, ulcers, bleeding, bloody scabs, etc.) or products that cause skin irritation (reversible damage).
ergonomic Serious eye damage / eye irritation | This class covers products that cause serious eye damage (i.e., tissue damage in the eye or serious physical decay of vision) or products that cause eye irritation (reversible damage).
general Respiratory or skin sensitization | A respiratory sensitizer is a product that may cause allergy or asthma symptoms or breathing difficulties if inhaled (hypersensitivity). Skin sensitizer is a product that may cause an allergic response after skin contact.
general Germ cell mutagenicity | This hazard class includes products that may cause or are suspected of causing heritable gene mutations (permanent changes (mutations) to body cells that can be passed on to future generations).
chemical Carcinogenicity | This hazard class includes products that may lead to cancer or may increase the incidence of cancer.
chemical Reproductive toxicity | This hazard class includes products that may damage or are suspected of damaging sexual function and fertility, have adverse effects on the unborn child (embryo, fetus, or offspring), or may have an effect on or through lactation (such as to cause harm to breast-fed children).
biological Specific target organ toxicity – single exposure | This hazard class covers products that cause or may cause damage to organs (e.g., liver, kidneys, or blood) following a single exposure. This class also includes a category for products that cause respiratory irritation or drowsiness or dizziness.
biological Specific target organ toxicity – repeated exposure | This hazard class covers products that cause or may cause damage to organs (e.g., liver, kidneys, or blood) following prolonged or repeated exposure.
chemical Aspiration hazard | Aspiration is defined as the entry of a liquid or solid into the trachea or lower respiratory system directly though the oral or nasal cavity, or indirectly by vomiting. In other words, aspiration occurs when instead of something going from your mouth or nose to your stomach (other than air), it enters the lungs. Serious health effects can occur such as chemical pneumonia, injury to the lungs, and death.
biological Biohazardous infectious materials | These materials are microorganisms, nucleic acids or proteins that cause or are a probable cause of infection, with or without toxicity, in humans or animals.
safety Health hazards not otherwise classified | This class covers hazards that are not included in any other health hazard class. These hazards occur following acute or repeated exposure and have an adverse effect on the health of a person exposed to them. The adverse effects include injuries or death of that person. If a product is classified in this class, the hazard statement will describe the nature of the hazard.

How will I know what hazard class or category is assigned to a hazardous product?

All hazardous products must be labelled according to the regulations, and must have a corresponding Safety Data Sheet (SDS). The hazard class and category will be provided in Section 2 (Hazard Identification) of the SDS. Each hazard class or category must use specific pictograms and other label elements to indicate the hazard that is present and what precautionary measures must be taken. Use the information provided by the label and SDS to be informed and to know how to safely use, handle, store and dispose of the hazardous product.