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What are the WHIMIS Symbols & What Do They Mean?

The Workplace Hazardous Materials Information System -- commonly known by its acronym, WHMIS -- is a Canadian inter-governmental system supporting safety in the workplace. While WHMIS includes many types of worker-education programs, one of its biggest components is the labeling of hazardous materials. The system has six lettered classes with accompanying symbols that are used to communicate different types of hazards associated with materials found in the workplace.

  1. Class A - Compressed Gases

    • The Class A symbol depicts a cylinder -- which represents the container for compressed gases -- surrounded by a circle. Any gas placed under chilled or pressurized conditions and contained in a cylinder falls into this category; examples include oxygen and propane. It's a hazard because the cylinder could explode if the gas inside expands due to high heat. Some compressed gases are so cold that a leak from a cylinder could cause frostbite.

    Class B - Flammable and Combustible Materials

    • The Class B symbol depicts flames surrounded by a circle, and represents materials that can catch fire easily. Flammable and combustible materials include not only solids, but gases such as propane and liquids like kerosene.

    Class C - Oxidizing Materials

    • The Class C symbol is a circle surrounding an "O" topped by flames. The symbol is found on "oxidizers" -- materials that can cause other things to to spontaneously combust, or that will feed a fire by providing oxygen. These can be gases, liquids or solids.

    Class D - Poisonous and Infectious Materials

    • While all items labeled Class D can cause bodily harm, this category is divided into three parts. The first is Materials Causing Immediate and Serious Toxic Effects, and is symbolized by a skull and crossbones surrounded by a circle. These materials can cause serious health issues -- and even death -- when humans are exposed to them. The second part is Materials Causing Other Toxic Effects, and is symbolized by a "T" that turns into an exclamation point, surrounded by a circle. This division includes materials that cause health issues, such as allergies, or even cancer, over long-term exposure. The last division is for Biohazardous Infectious Materials, and is depicted by a cluster of circles inside a larger circle. This part of the Class D category represents bacteria, viruses, parasites and fungi that may cause disease, such as the HIV virus.

    Class E - Corrosive Materials

    • The symbol for Class E items is a circle surrounding two test tubes dripping liquid over a solid item and a human hand. This label is for acids and similar materials that are capable of burning people, clothing, or other items.

    Class F - Dangerously Reactive Materials

    • Items in Class F are symbolized by a circle surrounding the letter "R" and a test tube. These labels are found on materials that must be handled very carefully, as they may react if they are shaken, warmed or cooled, pressurized, or mixed with another substance.

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