• Introduction
  • Class A
  • Class B
  • Class C
  • Class D
  • Class E
  • Class F
  • Review

Hazard Classification System

The WHMIS Hazard Classification System identifies six types, or broad classes of hazardous materials. Divisions are provided in some classes to separate different groups of hazardous materials within a class.

The classification system determines whether a product meets the criteria for inclusion in any of the WHMIS classes and is subject to the WHMIS information requirements.

Classification affects whether the product in included within WHMIS, but also the:

  • Content of labels, particularly hazard symbols, risk statements and precautionary measures.
  • Content of material safety data sheets, and
  • Instruction provided to workers.

 

A system of standardized symbols on WHMIS labels, each with a circular border, provides a uniform way to identify hazards. 

Reference to a product's class is found on the supplier label and sometimes on the MSDS.  The appropriate symbol must appear on all supplier WHMIS labels.

Suppliers must classify and evaluate their products in accordance with the hazard classes, which are identified in legislation.

Class A: Compressed Gas

The symbol for compressed gas is the outline of a compressed gas cylinder.
Compressed Gas

 

A compressed gas product is in a gaseous state and is kept under pressure.

Class A materials include compressed gases, dissolved gases or gases liquefied by compression or refrigeration.

Some compressed gases are also flammable and combustible. Others are also materials causing immediate and toxic effects. Whenever a controlled product falls into two or more classes, two or more hazard symbols are provided.

Hazards:

  • Explosion danger because the gas is being held under pressure;
  • Container may explode if heated in a fire;
  • Container may explode if dropped.
  • Severe injuries can be caused to unprotected skin and tissues when exposed to compressed gas.

 

Precautions:

  • Do not heat the container;
  • Keep container tightly closed;
  • Store containers in a properly designated area;
  • Handle with care.  Do not drop cylinder.
  • Wear Protective Equipment when using compressed gas
  • DO NOT blow compressed gas towards the body

 

Class B: Flammable and Combustible Material

The symbol for Flammable and Combustible is a flame.

This classification refers to a solid, liquid or a gas that will ignite and continue to burn if exposed to a flame or ignition.

Flammable materials will burn easily at or about room temperature (Flash point 38 degrees C or below) and Combustible material will burn when heated.

 

 

Six types of materials belong to this class:

  1. Flammable Gases: Examples propane and hydrogen. Flammable Liquids: Examples gasoline and BBQ starter fluid
  2. Combustible Liquids: Examples paint thinner and diesel fuel
  3. Flammable Aerosols: Examples hair spray, engine
  4. starter fluid and penetrating oil Reactive Flammable Materials: Examples celluloid and metallic sodium
  5. Combustible Solids: Examples; Wood and paper.
  

 

Hazards:

  • Will burn and is therefore a potential fire hazard;
  • May cause a fire when exposed to heat, sparks, or flames as a result of friction;
  • May burn at relatively low temperatures (flammable materials catch fire at lower temperatures than combustible materials).
  • Death and severe injuries due to burns and smoke and gas inhalation.
 

 

Precautions:

  • Store flammable material in a cool, fire-proof area;
  • Keep the material away from heat and ignition sources;
  • Keep container tightly closed;
  • Take precautionary measures against static discharges or impacts that could cause sparks.
  • When required, wear flame-resistant protective equipment
  

Class C: Oxidizing Materials

The symbol for Oxidizing Material is a flame above an "O", which stands for "Oxygen".

 

Oxidizing materials will cause or assist to cause fires in surrounding materials by supplying oxygen.

Oxygen is required for all fires, and any substance that increases the supply of oxygen will increase the chance of fires. Examples include: peroxide bleach, nitrites and chlorates.

  

 

Hazards:

  • May react violently;
  • Fire and /or explosion risk in the presence of flammable or combustible material;
  • May cause fire when it comes into contact with combustible materials such as paper;
  • May cause an explosion when it comes into contact with flammable material, such as fuel;
  • May burn skin and eyes upon contact.
  • Death and severe injuries due to burns and smoke and gas inhalation
 

 

Precautions:

  • Keep the material away from flammable and combustible materials;
  • Keep the material away from sources of heat and ignition;
  • Store containers in a proper designated area;
  • Avoid shock and friction;
  • Wear the proper protective equipment, including eye, face and hand protection, and protective clothing.
  • When required, wear flame-resistant protective equipment inhalation
 

Class D: Poisonous and Infectious Material

Materials that fall into Class D are further divided into three separate divisions:

 
  • D1
  • D2
  • D3

Class D1:Materials Causing Immediate and Serious Toxic Effects The symbol is the familiar skull and crossbones.

 

Examples include bleach, hydrogen sulphide, chlorine, strychnine and cyanides.

  

 

Hazards:

  • Potentially fatal poisonous substances;
  • May cause permanent damage if it is inhaled, swallowed or if it enters the body through skin contact;
  • May burn eyes or skin upon contact;
 

 

Precautions:

  • Store the material in designated areas only;
  • Handle the material with extreme caution; Do not breathe gas or vapours;
  • Avoid inhaling by working in well ventilated areas and/or wearing respiratory equipment;
  • Avoid contact with the skin or eyes by wearing the proper protective equipment, including eye, face and hand protection and protective clothing;
  • Wash and shower thoroughly after use.
 

Class D2: Materials Causing Other Toxic Effects

The symbol is a "T" made into an exclamation mark that stands for 'TOXIC'.

 

These are materials that may cause harmful effects usually some time after the first or repeated exposures. Examples include: vapours of solvents, mercury, some herbicides and aromatic solvents.

 

 

Hazards:

  • Poisonous, dangerous to health;
  • May cause permanent damage as a result of repeated exposures over time;
  • May cause death;
  • May cause birth defects or sterility;
  • May be a sensitizer, which produces an allergy;
  • May be a skin or eye irritant.
 

 

Precautions:

  • Store the material in designated places only;
  • Avoid inhaling by working in well ventilated areas and/or wearing respiratory equipment;
  • Avoid skin or eye contact by wearing all protective equipment necessary, including eye, face, and hand protection and protective clothing;
  • Wash thoroughly after use.
 

Class D3: Biohazardous and Infectious Material

This symbol looks like a cell that is dividing.

 

Biohazardous infectious materials are organisms (and the toxins of organisms) that cause diseases such as viruses, bacteria and fungi.

These organisms are frequently encountered in hospitals, laboratories and research facilities. Examples include: vaccines and science laboratory classes.

  

 

Hazards:

  • May cause a serious disease resulting in illness or death.
 

 

Precautions:

  • Handle the material in designated areas where engineering controls are in place to prevent exposure;
  • Handle the material only when fully protected by the proper, designated equipment;
  • Keep container tightly closed; Wear suitable protective equipment;
  • Take every measure to avoid contamination
 
 

Class E: Corrosive Material

The symbol for Corrosive material is liquid being poured onto a hand and a piece of solid material causing damage to the hand and the material.

Corrosive materials may cause burns and destroy tissues. They can also destroy other materials.

Examples: sulphuric acid, hydrochloric acid and anhydrous ammonia.

 

 

Hazards:

  • May be harmful if inhaled
  • Cause severe tissue damage on contact
  • Cause severe eye and skin damage on contact.
 

 

Precautions:

  • Keep containers tightly closed
  • Avoid inhaling by using in well ventilated areas and wear proper respiratory protection
  • Avoid skin and eye contact by wearing protective equipment, such as eye, face and hand protection and other protective clothing.
 

Class F: Dangerously Reactive Materials

The symbol is an exploding test tube inside a capital "R", which stands for "REACTIVE".

 

A substance is considered to be dangerously reactive when it will:

  • react with water to produce a poisonous gas
  • self-react if the container is heated, pressurized, or shaken; or
  • self-react because of age.
 

 

Hazards:

  • Very unstable material; May explode as a result of shock, friction or increase in temperature;
  • May explode if heated when in a closed container;
  • May undergo vigorous polymerization;
  • May react with water to release toxic or flammable gas
 

 

Precautions:

  • Store the material in a cool, flame-proof area; Keep the materials away from heat;
  • Open containers carefully, do not drop them; Avoid contact with water;
  • Avoid shock and friction;
  • Wear suitable protective clothing.
 

There are four "self-test" questions for this section.  If you think you're ready, go to Question 1 now.  If you think you'd like another look at the content before you test yourself, go back to the beginning of the module.

  • Q1
  • Q2
  • Q3
  • Q4
  • a
  • b
  • c
  • d
  • e
  • f
  • g
  • h

Question #1a

Click on the hazard symbol that represents Biohazardous and Infectious Materials

 

Option 1

1

Option 2

2

Option 3

3

Option 4

4
 
 

Option 5

5

Option 6

6

Option 7

7

Option 8

8

Question #1b

Click on the hazard symbol that represents Compressed Gas

 

Option 1

1

Option 2

2

Option 3

3

Option 4

4
 

 

Option 5

5

Option 6

6

Option 7

7

Option 8

8

Question #1c

Click on the hazard symbol that represents Corrosive Materials

 

Option 1

1

Option 2

2

Option 3

3

Option 4

4
 

 

Option 5

5

Option 6

6

Option 7

7

Option 8

8

Question #1d

Click on the hazard symbol that represents Dangerously Reactive Materials

 

Option 1

1

Option 2

2

Option 3

3

Option 4

4
 

 

Option 5

5

Option 6

6

Option 7

7

Option 8

8

Question #1e

Click on the hazard symbol that represents Flammable and Combustible Materials

 

Option 1

1

Option 2

2

Option 3

3

Option 4

4
 

 

Option 5

5

Option 6

6

Option 7

7

Option 8

8

Question #1f

Click on the hazard symbol that represents Materials Causing Immediate and Serious Toxic Effects (poisonous)

 

Option 1

1

Option 2

2

Option 3

3

Option 4

4
 

 

Option 5

5

Option 6

6

Option 7

7

Option 8

8

Question #1g

Click on the hazard symbol that represents Materials Causing Other Toxic Effects

 

Option 1

1

Option 2

2

Option 3

3

Option 4

4
 

 

Option 5

5

Option 6

6

Option 7

7

Option 8

8

Question #1h

Click on the hazard symbol that represents Oxidizing Materials

 

Option 1

1

Option 2

2

Option 3

3

Option 4

4
 

 

Option 5

5

Option 6

6

Option 7

7

Option 8

8

Question #2

Materials that fall into class D (Poisonous and Infectious Materials) are further divided into three separate divisions. Indicate which of the following are Class D divisions:

 
  1. Materials causing Immediate and Serious Toxic Effects

Question #3

This symbol represents

 

  • a
  • b
  • c

Question #4a

Oxygen is NOT absolutely essential for combustion.

 

A. TRUE

B. FALSE

Question #4b

Biohazardous and Infectious Materials may cause serious disease resulting in illness or death.

 

A. TRUE

B. FALSE

Question #4c

The Hazardous Symbols are legible pictograms surrounded by square borders.

 

A. TRUE

B. FALSE