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Fire Classes Information

 

There are five main classes of fire:

Class A - Ordinary Combustibles

Class A Fires are fires containing ordinary combustible materials, including wood, cloth, paper, rubber, and some plastics. These are generally extinguished by the heat-absorbing  (cooling) effects of water, the coating effects of certain dry chemicals which exclude air, or the interruption of the combustion chain reaction by halogenated agents.

a.    Wood, paper, cardboard, fabric

b.    Ordinary garbage

 

Class B - Flammable Liquids and Gases

Class B Fires are those on flammable or combustible liquids, flammable gases, greases and similar materials. They are generally extinguished by excluding air, inhibiting the release of combustible vapours, or interrupting the combustion chain reaction.

A  water extinguisher should never be used to extinguish this type because it can cause the fuel to scatter, spreading the flames. The most effective way to extinguish a liquid or gas fueled fire is by inhibiting the chemical chain reaction of the fire, which is done by dry chemical or clean agent extinguishing agents, although smothering with CO2 or, for liquids, foam is also effective.

Examples:

a.    Gasoline

b.    Oils

c.    Paints

d.    Propane

e.    Kerosene

f.     Paraffin

 

Class C - Fires on Electrical Equipment - with Power

Class C Fires can be any of the other types of fires, but where electrical equipment is involved - with power.

 

They are fires in live electrical equipment where there is potential electrical shock hazard.

 

Agents used on these fires must be non-conductive, such as a dry chemical, carbon dioxide or halogenated agents. Therefore water extinguishers must NOT be used as they can conduct electricity and risk shock to people. 

 

Class D - Fires on Combustible Metals and Alloys

A Class D fire is including the presence of burning metals. Only certain metals are flammable.

Examples of combustible metals are sodium, potassium, uranium, lithium, plutonium, with the most common Class D fires involving magnesium and titanium. Some combustible metals such as Sodium burn when in contact with air (or water). 

Class D fires require a heat-absorbing extinguishing medium that does not react with the burning metals. Water extinguishers should not be used as they can spread and further activate the fire, making it worse. 

 
 

Class K - Fires on Cooking Materials

A Class K fire is really a sub-class of Class B - Flammable Liquids and Gases

Class K is for unsaturated cooking oils in well-insulated cooking appliances located in commercial kitchens.

Water extinguishers with a solid water stream should not be used as they can spread and further activate the fire, making it worse. However, water mist extinguishers can be effective in some cases. The most effective extinguishing agents are special foam (Type K) extinguishers. Fire blankets can also be used effectively. 

It is mandatory for commercial kitchens to have Fire Suppression systems, and a Type K fire extinguisher

Examples:

a.    Cooking Oils

b.    Animal and vegetable fats

c.    Grease