Thompson Rivers University
Thompson Rivers University

Symbol Classification

WHMIS Symbol Classification

Classes and Symbols WHMIS covers six broad types, or classes of hazardous materials which are lettered A through F. Divisions are provided in some classes to separate different groups of hazardous materials within a class. Symbols are used for these different types of hazardous materials as follows:

gas Class A: Compressed Gas
This class includes compressed gases, dissolved gases and gases liquified by compression or refridgeration. Examples: gas cylinders for oxyacetylene welding or water disinfection
flammable Class B: Flammable and Combustible Material
Solids, liquids and gases capable of catching fire or exploding in the presence of a source of ignition. Examples: white phosphorus, acetone and butane. Flammable liquids such as acetone are more easily ignited than combustible liquids such as kerosene.
oxidize Class C: Oxidizing Material
Materials which provide oxygen or similar substances and which increase the risk of fire if they come into contact with flammable or combustible materials. Examples: sodium hypochlorite, perchloric acid, inorganic peroxides.
skull Class D: Poisonous & Infectious Materials
Class D, Division 1

Materials causing immediate and serious toxic effects. This division covers materials which can cause the death of a person exposed to small amounts. Examples: sodium cyanide, hydrogen sulphide.
toxic Class D, Division 2
Materials causing other toxic effects. This division covers materials which cause immediate eye or skin irritation as well as those which can cause long-term effects in a person repeatedly exposed to small ammounts. Examples: acetone (irritant), asbestos (carcinogen), toluene diisocyanate (senzitizer).
biohaz Class D, Division 3
Biohazardous infectious material. This division applies to materials which contain harmful microorganisms. Examples: cultures or diagnostic specimens containing salmonella bacteria or the hepatitis B virus
corrosive Class E: Corrosive Material
Acid or caustic materials which can destroy the skin or eat through metals. Examples: muriatic acid, lye.
reactive Class F: Dangerously Reactive Material
Products which can undergo dangerous reaction if subjected to heat, pressure, shock or allowed to contact water. Examples: plastic monomers such as butadiene and some cyanides.

If a WHMIS product is contained or transferred in:

  1. a pipe or piping system
  2. a process or reaction vessel
  3. a conveyor belt, tank car, ore car or similar

An employer can use numbers, letters and colours in addition to, or in place of, the symbols above. If this option is used all workers must be aware of the alternate identification method.