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What Is WHMIS Classification?

WHMIS stands for Workplace Hazardous Materials Information System. WHMIS is a system developed by the Canadian government for communicating hazards about dangerous substances to the users of those materials. As part of this system, all hazardous substances are placed into different classifications according to their specific dangers. It is a legal requirement for the producers and users of such materials in Canada to follow the WHMIS process.

  1. Classification

    • A hazardous substance under WHMIS is defined as one that is referenced in the Canadian government's Controlled Products Regulations and is not exempt under the Hazardous Products Act. The producer or importer of a chemical must have the product undergo a series of testing as specified in the regulations to determine if it is a controlled product, as well as what classification it fits into. A product may fit into more than one classification. Examples of exempt products covered under different legislation are radioactive materials and explosives.

    Class A

    • Controlled products in Class A are given the classification of compressed gases. Propane tanks and cylinders of acetylene are included in this classification. The symbol is a drawing of an angled gas cylinder.

    Class B

    • Class B chemicals are in the category of flammable or combustible material. These compounds can be solids, liquids or gases. Flammable compounds give off enough vapors to start a fire at temperatures below 100 degrees Fahrenheit, whereas combustible materials have to be heated to between 100 and 200 degrees. Common solvents like acetone and paint thinner go into this class, along with gases like propane and butane. The symbol for this class is a flame.

    Class C

    • Class C chemicals are oxidizing materials. These are chemicals that contain readily available oxygen and can form highly combustible mixtures with various fuel sources; they also greatly increase the rate of a combustion reaction. Examples include ammonium nitrate and nitric acid. The symbol for this class is a flaming letter "O."

    Class D

    • This category contains poisonous and infectious materials, and it has three divisions. Division D1 contains materials producing immediate and serious toxic effects and has the symbol of a skull and crossbones. Division 1 has two subdivisions. Subdivision D1A substances are classed as very toxic; these are poisons like cyanide and arsenic. D1B compounds are classed as toxic and include less dangerous poisons, where a larger dose is required for serious effects. D2 products are those that cause other toxic effects; the symbol is a large letter "T," the base of which transitions into an exclamation point. It too has two subdivisions. D2A materials are very toxic; some cause cancer and birth defects. D2B are toxic and can produce allergic reactions or irritation. D3 are biohazardous infectious materials, such as blood, viruses and bacteria. The symbol for D3 is a small central circle with three "C" shapes facing out from its middle.

    Class E

    • Chemicals in Class E are corrosive, meaning they can produce chemical burns on skin or other materials, such as metal. This includes acids like hydrochloric acid, bases like sodium hydroxide and some other chemicals, such as chlorine. The symbol consists of a horizontal bar and a hand, both being damaged by having a corrosive liquid poured on them.

    Class F

    • Class F materials are classified as dangerously reactive. These are substances that are essentially unstable. They must meet one of three criteria: The material either reacts vigorously with water to produce toxic gas, reacts with itself if jolted or heated, or polymerizes or decomposes violently. An example is ethylene oxide. This class is given the symbol of a fuming test tube superimposed over a large "R."

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