The Different WHMIS Chemical Classifications

The Workplace Hazardous Materials Information System (WHMIS) is Canada’s national workplace hazard communication standard. This legislation applies to all workers involved in manufacturing, or work with or are in proximity to controlled substances or products in their place of work. The WHMIS is a comprehensive plan that provides information on the safe use of hazardous materials. These safety information are delivered to the involved personnel by means of:

  • Cautionary labels found on the containers of controlled products
  • Providing material safety data sheets (MSDS) for each controlled product; and
  • Educating workers and providing site-specific training programs on hazardous substances

Exposure to hazardous substances can cause or contribute to various serious health issues such as dizziness, lung or kidney damage, cancer, sterility, burns, and rashes. Some hazardous materials are also safety hazards, and can cause fire or explosions. WHMIS was established to help prevent injuries, illnesses, deaths, medical costs, and fires caused by hazardous products. The end goal is to create a safer workplace by making sure you and your workers are knowledgeable about these hazards and have the proper tools to work safely.

WHMIS has established eight different classes to identify chemical hazards. Each class has a corresponding symbol for identification:

whmis_a (1)Class A (Compressed Gas)

Compressed gas is any gas placed under constant pressure or chilled, contained by a cylinder. A sudden release of high pressure can be deadly; it can puncture the skin and cause fatal embolism. Heat exposure can also cause it to explode. Leaking cylinders are also a danger because the gas that comes out may cause frostbite. Compressed gas includes carbon dioxide, oxygen, compressed air, ethylene, and welding gases. The hazard symbol is an image of a cylinder surrounded by a circle.

whmis_bClass B (Flammable and Combustible Material)

Any material that will burn, explode, or catch fire easily at normal temperature (below 37.8 °F) are considered flammable. Combustible materials must be heated first before they will ignite while reactive flammable materials are those that suddenly start burning when it touches air or water. Materials under this class can be solid, liquid or gas such as acetone, turpentine, ethanol, propane, butane, kerosene, spray paints, and varnish. The symbol for this is a flame with a line under it inside a circle.

whmis_cClass C (Oxidizing Material)

Oxygen is necessary for combustion. Oxidizers do not burn but can cause other materials that normally do not burn to suddenly catch fire by providing oxygen. They can be in the form of gases such as oxygen and ozone, liquids such as nitric acids and perchloric acid solutions, or solids such as sodium chlorite. The symbol for oxidizing materials is an “o” with flames on top of it inside a circle.

whmis_d1Class D – Division 1 (Poisonous & Infectious Material, Immediate Serious Toxic Effects)

Materials under this division are very poisonous and can cause immediate death or serious injury if inhaled, digested, absorbed, or injected into the body. Most Class D-1 materials will also cause long term effects. Some examples of D-1 materials include sodium cyanide, carbon monoxide, sulphuric acid, acrylonitrile, and 4-diisocyanate (TDI). The symbol is a skull and crossbones inside a circle.

whmis_d2Class D – Division 2 (Poisonous & Infectious Material, Other Toxic Effects)

These are poisonous materials as well but their effects are not as quick-acting and only temporary. Those that don’t have immediate effects may still have serious results such as cancer, liver or kidney damage, birth defects, or reproductive problems. Some of these materials include asbestos, mercury, benzene, acetone, and cadmium. The symbol for Class D-2 looks like a “T” with an exclamation point at the bottom inside a circle.

whmis_d3Class D – Division 3 (Poisonous & Infectious Material, Biohazardous Infectious Material)

These are toxins or organisms such as viruses, bacteria, fungi, and parasites, that can cause diseases in people or animal. Biohazardous infectious materials are usually found in hospitals, laboratories, healthcare facilities, veterinary practices, and research facilities. Any person handling specimens or samples in these environments should assume that they are contaminated and should treat them accordingly. Examples of these materials include Hepatitis B, AIDS/HIV virus, and salmonella. A Class D-3 symbol looks like three “c”s joined together with a small circle in the middle, all inside a circle.

whmis_eClass E (Corrosive Material)

Corrosive materials, such as acids and bases will burn eyes and skin on contact. It can also cause irreversible damage to human tissue such as the eye or lung. It will also attack clothes and other materials like metal. Common corrosive materials include sulphuric and nitric acids, ammonium hydroxide, and caustic soda. The symbol for Class E is an image of two test tubes pouring liquid on a bar and a hand inside a circle.

whmis_fClass F (Dangerously Reactive Material)

Materials under this class  are unstable, and may burn, explode or produce dangerous gases when mixed with incompatible materials. A Class F material manifests three different properties or abilities:

  1. It can react very strongly and quickly with water to make toxic gas;
  2. It will react with itself when it gets shocked, or if the temperature or pressure increase; and
  3. It can undergo polymerization, decomposition, or condensation.

Examples of this class include vinyl chloride, ethyl acetate, ethylene oxide, and picric acid. The symbol for this class is a picture of a test tube with sparks coming out of the tube surrounded by a letter “R” inside a circle.

A safe environment is important for everyone, and knowing how to properly handle hazardous materials in your facility is one way to achieve that. A thorough WHMIS education coupled with a strong PPE training program will help you in achieving a safe and efficient workplace.


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