There are five different types of fires, and each needs be put out using different extinguishing agents. If you went into a restaurant kitchen, a steel factory and a paint store, for instance, you would see three different types of extinguishers (a Class K, Class D and Class B, respectively). In this article, the fire safety experts at Guard-X will tell you about the five types of fires and how they’re extinguished.

1. Class A fire. This type of fire involves organic solids such as wood, paper, fabric and plastic. It can be fast-flaming, which is to say caused by the ignition of flammable materials producing immediate flames. Or, it can be a slow-starting smoldering fire: a slow, low-temperature, flameless form of combustion that becomes a flaming fire in the presence of a combustive, such as oxygen (even a weak current of air can spark a flame). To put out a Class A fire, the heat needs to be extinguished and the source of oxygen eliminated.

2. Class B fire. This type of fire involves flammable liquids, such as grease, oils, tars, oil-based paints, solvents, lacquers and alcohols. Unlike Class A fires, they never involve smoldering, and quashing the flames will fully put out the fire.

3. Class C fire. This type of fire involves electrical equipment such as televisions, appliances, computers, motors and transformers. It presents a risk of electrocution and should be extinguished by professionals.

4. Class D fire. This type of fire involves combustible metals, such as magnesium, titanium, zirconium, sodium, lithium and potassium. Usually violent and extremely bright, Class D fires primarily occur in the industrial sector.

5. Class K fire. This type of fire involves cooking oils and greases such as animal and vegetable fats. Because of the high flash point of these liquids, a different extinguishing agent is required for Class K fires than the one used for Class B fires.

Each type of fire can only be extinguished using the correct extinguishing agent. Water, powder, foam and CO2 are the main products used to put out fires.

Water cools, disperses and stifles fire. It’s used for Class A fires. It shouldn’t be used to put out the other types of fires, as it could cause explosions or result in electrocution.

Powder inhibits flames and prevents them from spreading. There are multi-purpose powder fire extinguishers for Class A, B and C fires on the market.

Foam is reserved for firefighters, who use it primarily for class B fires.

CO2 is a gaseous extinguishing agent that stifles and isolates fire. It is used for Class B and C fires.

Fire extinguishers are labelled according to what class or classes of fires they’re designed to put out.

How are Class D fires extinguished?

Class D fires are less common that Class A and B fires but can be just as destructive. They can’t be extinguished with water, and in fact, water only energizes the flames. The most effective way to fight a Class D fire is with dry-powder extinguishing agents, which absorb the heat and smother the flames.

How are Class K fires extinguished?

Similar to Class B fires, you should never spray Class K fires with a solid stream of water, as this can cause the fuel to scatter and spread the flames. The proper extinguisher to use is a wet chemical extinguisher, which uses a foam-forming agent to prevent the fire from reigniting.

What do I do in the event of a fire?

When a fire occurs, the first thing to do is sound the fire alarm and call the fire department. Only attempt to put out the fire if it’s small and isn’t quickly spreading. Otherwise, evacuate the area.

Before beginning to extinguish a fire, identify a safe evacuation path. Don’t allow the fire, heat, or smoke to come between you and your evacuation path. Stand at least three metres away from the flames when using the extinguisher.

To operate an extinguisher, use the PASS technique:

P: pull the pin.
A: aim low, pointing the nozzle at the base of the fire.
S: squeeze the handle to spray the extinguishing agent.
S: sweep from side to side at the base of the fire until it fully extinguishes.

When the fire is out, continue to watch the area, as the fire could reignite.

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