CLASSES OF FIRE & EXTINGUISHERS

Firefighting and Safety Guide

When a fire breaks out in your home, office, or business, a fire extinguisher or any immediate fire suppression products should be on hand to put out, mitigate, or at least delay the spread of the fire.

Home, business, or building owners wrongly assume that all fires are the same and, with that scant knowledge, assume that any type of fire extinguisher or suppressant can be used to fight a fire. That is not the case!

It’s therefore imperative that you have knowledge of the different classes of fires, their likelihood, and the types of fire extinguishers needed for that purpose. Using the wrong extinguishing agent can exacerbate the problem further.

With this in mind, let’s look at the different classes of fire and what extinguishing agents ought to be used for each class.

Classes of Fire and Fire Extinguishers

Class A Fire

This is a type of fire that involves or is caused by ordinary combustible solids such as cardboard, textiles, wood, or paper, among others.

Class A fires can be extinguished by water extinguishers. The water cools the burning material to temperatures below the ignition point.

Class B Fire

Class B fires can be caused by volatile or flammable liquids such as gasoline, grease, turpentine, oil, and even paint.

Class B fires can be suppressed by dry chemical powder extinguishers, which smother the fire, halting the chain reaction.?

Class C Fire

These are fires that involve flammable gases, usually found in gas canisters and cylinders, such as hydrogen, methane, butane, or propane.

These fires are best tackled with carbon dioxide extinguishers, which are also used for electrical fires.

Class D Fire

This is a fire that usually breaks out in industrial environments and involves combustible metals such as sodium, magnesium, aluminum, potassium, and titanium, among others.

Class D fires are fought using specialized dry powder extinguishers that smother the fire and prevent the metal from reigniting.

Class E Fire (Electrical)

These are electrical fires, i.e., they’re caused by electrical equipment and appliances, including transformers and motors.

Class C fires are best tackled with CO2 (carbon dioxide) extinguishers, as they remove or displace oxygen needed for combustion. They are usually used for close-range firefighting.

But once the electrical appliance or equipment has been removed, the fire changes class.

Class F Fire

These fires are common in kitchens and cooking areas and involve cooking oils, fats, and agents usually found in or originating from deep-fat fryers and pans.

Wet chemical extinguishers should be used to fight class K fires, as they create a layer of foam over the burning oil, cutting off oxygen from the atmosphere, which chokes the fire.

Fire Extinguishers

Water Extinguishers

They’re the most common type of extinguisher and are used for fighting fires involving ordinary combustible solids. The water cools down the fuel or burning solids until the fire is eventually extinguished or falls below the combustion point.

Most premises, e.g., schools, offices, residential houses, and warehouses, can be equipped with either foam or water fire extinguishers. They have a bright red label.

Water spray and water mist extinguishers also fall into this category.

They should be located on a floor where a Class A fire risk has been identified.?

Water-based extinguishers should never be used for oil-based fires or electrical firefighting!

Foam Fire Extinguishers

These are also water-based extinguishers and are used to put out Class A and B fires by creating a foam layer over the burning (flammable) liquid or solid and cutting off oxygen supply.

They can be used in offices, homes, schools, and buildings where flammable liquids are stored. They have a cream label.

Like water extinguishers, they should not be used for fires involving electrical equipment, combustible metals, or kitchen fires.

They should also be placed on exits on floors where the risks of class A and B fires have been identified.

Co2 (Carbon Dioxide) Extinguishers

They can be used to put out Class B and E (Electrical) fires.

They’re usually found in server or electrical equipment rooms or anywhere where electrical equipment is used, e.g., offices, construction sites, kitchens, labs, and even vehicles. They have a black label.

They ought to be placed near the source of the fire risk and/or near exits.

They should not be used for kitchen oil or grease fires, flammable metals, or combustible solids like wood, textiles, or paper.

Wet Chemical Extinguishers

These are mainly used in industrial and commercial kitchens to put out fire from cooking oils and fats. They spread a foam over the burning fat or oil, cutting off oxygen as well as cooling the fuel.

They have a yellow label.

They should be placed close to the source of the fire risk.

They should not be used for flammable liquids or gases, flammable metals, or electrical fires.

Dry Powder Extinguishers

Dry powder extinguishers can be considered one-in-all extinguishers as they can put out a variety of fires, i.e., A, B, C, D, and even E classes of fire. They smother fires by creating a barrier between the burning material and the oxygen supply.

They can be used on premises where activities like welding, LPG gas dispensing, and chemical processing with flammable gases take place. They have a blue label.

They should be located close to the source of the fire risk.

They’re not recommended for enclosed spaces since the powder can be harmful when inhaled. They should also not be used for kitchen fires involving cooking oil or for fires involving electrical equipment exceeding 1000 volts.

In the case of flammable metals, specialized dry chemical powder extinguishers are recommended, though.

Conclusion

Having the right type of fire extinguisher can make a difference in the effectiveness of fighting and mitigating the effects of a fire.

Using the wrong extinguisher and unsafe firefighting practices can exacerbate the problem as well as expose a firefighter to a risk of injury, some of which can be fatal.

Prevention is always better than cure. While extinguishers are important for putting out fires or minimizing loss, taking measures to prevent fire outbreaks should be the priority.