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As you saw in the last lesson, household products that may pose a danger if used incorrectly are labelled with symbols to warn consumers about those dangers. In a similar way, chemical products used in the workplace are also labelled with various symbols depending on the possible reactions that the chemicals might cause.

WHMIS groups products with similar properties or hazards into classes. The Controlled Products Regulations specifies the criteria used to place materials within each classification. WHMIS classifications are made by the manufacturer or supplier for products to be used in Canada.

These are the WHMIS symbols that you might see on different products:

Class A: Compressed Gas

Some common materials that have this WHMIS symbol on the container are propane tanks of various sizes as well as oxygen and acetylene in cylinders used for welding. These cylinders might explode if exposed to heat or if dropped.

Class B: Flammable and Combustible Material

This symbol is placed on products that could start a fire if a spark or flame occurs near them. Some examples of flammable and combustible materials are butane, propane, gasoline, kerosene, aerosols, and even some types of metals.

Class C: Oxidizing Material

This symbol is placed on products that increase the risk of fire if they are in contact with flammable or combustible materials. Some materials that have this label are hydrogen peroxide (used in the pulp and paper industry), compressed oxygen (used in hospitals), and some acids.

Class D-1: Poisonous and Infectious Material Causing Immediate and Serious Toxic Effects

Products with this label can kill or cause serious illness very quickly, even in small amounts. Examples of this type or product are sodium cyanide (used in extracting precious metals from ore) and hydrogen sulphide (used in manufacturing chemicals, dyes, rubber, rayon, etc.).

Class D-2: Poisonous and Infectious Material Causing Other Toxic Effects

Products with this label can cause serious long-term health problems such as cancer as well as more immediate problems such as irritation of the eyes and skin. Products that have this label include asbestos (used in insulation) and xylene (used in cleaners and paint thinners).

Class D-3: Biohazardous Infectious Material

Products with this label contain micro-organisms that can cause illnesses such as hepatitis or salmonella (food poisoning).

Class E: Corrosive Material

This label is placed on containers of chemicals that can eat through skin or other materials. Some examples are hydrochloric acid (used in processing steel, making batteries, and many other processes) and nitric acid (found in fertilizers).

Class F: Dangerously Reactive Material

Products with this label may explode or emit toxic gas. Cyanide (used in manufacturing paper, textiles, and plastics) has this label.

Sometimes WHMIS labels are printed in colour: red for fire, blue for poison, and yellow for "change." In this case, Class A, C, and F materials are yellow, Class B materials are red, and Class D and E materials are blue.

Click on the Play button below to watch a video on WHMIS symbols.