Hazard Symbols

Hazard Symbols

The WHMIS 2015 system groups hazardous materials into two major hazard groups: physical hazards and health hazards. Physical hazards are based on the physical and/or chemical properties of the product, while health hazards are based on the ability of the product to cause a health effect. These two hazard groups are further divided into hazard classes, which allows for grouping of products that share similar properties.

Physical Hazards

The physical hazards group includes the following hazard classes:

  • Combustible dusts
  • Corrosive to metals
  • Flammable aerosols
  • Flammable gases
  • Flammable liquids
  • Flammable solids
  • Gases under pressure
  • Organic peroxides
  • Oxidizing gases
  • Oxidizing liquids
  • Oxidizing solids
  • Pyrophoric gases
  • Pyrophoric liquids
  • Pyrophoric solids
  • Self-heating substances and mixtures
  • Self-reactive substances and mixtures
  • Simple asphyxiants
  • Substances and mixtures which, in contact with water, emit flammable gases
  • Physical hazards not otherwise classified

Health Hazards

The health hazards group includes the following hazard classes:

  • Acute toxicity
  • Aspiration hazard
  • Biohazardous infectious materials
  • Carcinogenicity
  • Germ cell mutagenicity
  • Reproductive toxicity
  • Respiratory or skin sensitization
  • Serious eye damage/eye irritation
  • Skin corrosion/irritation
  • Specific target organ toxicity-single exposure
  • Specific target organ toxicity- repeated exposure
  • Health hazards not otherwise classified

Hazard Classes

The following are brief descriptions of hazard classes that a hazardous product can be classified under.

The physical hazard classes are listed first, followed by the health hazard classes.

Physical Hazard Class  General Description 

Flammable gases;

Flammable aerosols;

Flammable liquids; Flammable solids

These four classes include products that have the ability to ignite (i.e. catch fire) easily. Explosion or fires are the main hazards.
Oxidizing gases; Oxidizing liquids;

Oxidizing solids

These three classes include oxidizers, which may cause or intensify a fire or explosion.
Gases under pressure This class includes compressed gases, liquefied gases, dissolved gases and refrigerated gases. Compressed, liquefied, and dissolved gases are hazardous because of the high pressure contents of the cylinder/container. The cylinder/container may explode if heated. Refrigerated liquefied gases are very cold and can cause severe cold burns and/or injury.
Self-reactive substances and mixtures This class includes products that may react on their own, or if heated, and cause a fire or an explosion.
Pyrophoric liquids; Pyrophoric solids This class includes product that can spontaneously catch fire if exposed to air.
Self-heating substances and mixtures This class includes products that may catch fire if exposed to air. These products differ from pyrophoric liquids or solids because they will only ignite after a longer period of time or when present in large quantities.
Substances and mixtures which, in contact with

water, emit flammable gases

This class includes products that react with water and releases flammable gases. Sometimes, the flammable gases spontaneously ignite.
Organic peroxides This class includes products that are highly reactive, unstable, and/or explosive. If heated, these products may cause a fire or an explosion.
Corrosive to metals This class includes products that may be corrosive (i.e. chemically damaging and/or destructive) to metals.
Combustible dusts This class warns about products that are finely divided solid particles. If dispersed in air, the particles may catch on fire or explode if ignited.
Simple asphyxiants This class includes products which are gases that may displace the oxygen in the air and cause suffocation.
Physical hazards not otherwise classified This class includes products that cause physical hazards that are not covered in any of the other physical hazard classes. These hazards involve chemical reactions that can cause serious injuries or death. If a product is classified under this class, the nature of the hazard will be described in the hazard statement on the label and SDS.
Health Hazard Class
Acute toxicity This class includes products that are fatal, toxic, or harmful if inhaled, if in contact with skin, or if swallowed.
Skin corrosion/irritation This class includes products that cause severe skin burns (i.e. corrosion) and products that cause skin irritation.
Serious eye damage/eye irritation This class includes products that cause serious eye damage (i.e. corrosion) and products that cause eye irritation.
Respiratory or skin sensitization This class includes products which are classified as a respiratory or skin sensitizer. Respiratory sensitizers are products that may cause allergy or asthma symptoms and/or cause breathing difficulties when inhaled. Skin sensitizers are products that may cause an allergic skin reaction.
Germ cell mutagenicity This class includes products that may cause or are suspected of causing genetic defects.
Carcinogenicity This class includes products that cause or are suspected of causing cancer.
Reproductive toxicity This class includes products that may damage or are suspected of damaging fertility and/or the unborn child.
Specific target organ toxicity- single exposure This class includes products that cause or may cause damage to organs (e.g., liver, kidneys, or blood) following a single exposure.
Specific target organ toxicity- repeated

exposure

This class includes products that cause or may cause damage to organs (e.g., liver, kidneys, or blood) following prolonged or repeated exposure.
Aspiration hazard This class includes products that may be fatal if they are swallowed and/or enter the airways.
Biohazardous infectious materials This class includes products which are micro-organisms (e.g., viruses, bacteria, or fungi), nucleic acids (e.g., DNA or RNA), or proteins that cause or probable causers of infection, with or without toxicity, in humans or animals.
Health hazards not otherwise classified This class includes products that cause health hazards that are not included in any other health hazard class. These hazards occur following acute or repeated exposure and have adverse effects on the health of a person exposed to them -including injury or death. If a product is classified under this class, the nature of the hazard will be described in the hazard statement on the label and SDS.

Hazard Categories

Each hazard class contains at least one hazard category. The hazard category is assigned a number (e.g. 1, 2 etc.). Hazard categories can also be called a “type”; each type is assigned an alphabetical letter (e.g. A, B etc.). Subcategories are identified by the assigned number and letter (e.g. 1A or 1B etc. ).

The hazard category informs the reader of how hazardous the product is:

  • Category 1 is always the most hazardous within that class. If Category 1 is further divided, then Category 1A is more hazardous than Category 1B, within the same hazard class.
  • Category 2 within the same hazard class is more hazardous than Category 3, and so on.

Note: There are a couple of exceptions to this rule.

  1.  Under the “Gases under pressure” hazard class, the hazard categories for this class are: “Compressed gas”, “Liquefied gas”, “Refrigerated liquefied gas”, and “Dissolved gas”. In this case, the classes are indicative of the physical state of the gas when packaged rather than the degree of hazard of the product.
  2. Under the “Reproductive toxicity” hazard class, there is an “Effects on or via lactation”. This category is not assigned a specific numbered category. This hazard class does have categories 1 and 2, which refers to effects on fertility and/or the unborn child. In this case, “Effects on or via lactation” is considered to be a related but different hazard that falls under the “Reproductive toxicity” hazard class.

Pictograms

Pictograms are graphic images that allows for immediate classification of the type of hazard a hazardous product presents. WHMIS 2015 has revised and updated the pictograms that have been assigned to specific hazard classes or categories. Apart from the biohazardous infectious material pictogram, all pictograms used in WHMIS 2015 have a distinctive red, diamond-shaped border. Inside the border is the symbol that represents the potential hazard posed by the product.

The following table lists the pictogram and the hazard it represents.

Material Safety Data Sheets (MSDSs)