Fire Extinguisher| It's Types and Uses

Fire Extinguisher

Fire extinguishers are portable devices used to extinguish small fires or reduce their destruction before firefighters arrive at the scene. These are kept handy at places, namely fire points, in buildings, factories, public paces or transportation. The types and numbers of extinguishers legally required for an area are governed by the safety regulations in force in that particular area.

Types Of Fire Extinguishers

No single extinguisher can be used to tackle every fire, and because each type of fire extinguisher has different classes of fire on which it is effective, selection can be a minefield.

The first step is to look at what materials are present in the area to be protected from fire. These can be divided into six categories of fire involving different substances:

• Class A, combustible carbon-based solids eg paper, wood, or textiles

• Class B, flammable liquids eg paraffin, petrol, diesel or oil (but not cooking oil)

• Class C, flammable gases, eg butane, propane, or methane

• Class D, burning metals, eg aluminum, lithium, or magnesium

• Fires caused by electrical equipment (indicated by an electric spark symbol and not the letter E)

• Class F, fats, and cooking oils.

Fire Extinguisher Types Chart

This chart visualizes the fire extinguisher types and the types of fire for which they are suitable. 

Figure 1 The expression of the Types of Fire Extinguishers w.r.t the Types of Fire

• Dry Powder Fire Extinguishers

Dry powder extinguishers are similar to dry chemical extinguishers except that they extinguish the fire by separating the fuel from the oxygen element or by removing the heat element of the fire triangle.

Dry powder extinguishers are for Class D or combustible metal fires ONLY. They are ineffective on all other classes of fires. 

• Water and Foam Fire Extinguishers

Water and foam fire extinguishers extinguish the fire by taking away the heat element of the fire triangle. Foam agents also separate the oxygen element from the other elements.

Water extinguishers are for Class A fires only; they should not be used on Class B or C fires. The discharge stream could spread the flammable liquid in a Class B fire or could create a shock hazard on a Class C fire. 

• Water Mist Fire Extinguishers

Water mist extinguishers put out fires by taking away the heat element of the fire triangle. They are an alternative to the clean agent extinguishers where contamination is a concern.

Water mist extinguishers are primarily for Class A fires, although they are safe for use on Class C fires as well.

• Carbon Dioxide Fire Extinguishers

Carbon dioxide fire extinguishers extinguish fire by taking away the oxygen element of the fire triangle, and by removing the heat with a very cold discharge.

Carbon dioxide extinguishers can be used on Class B and C fires. They are usually ineffective on Class A fires. 

• Clean Agent Fire Extinguishers

Halogenated or clean agent extinguishers include the halon agents as well as the newer and less ozone depleting halocarbon agents. They extinguish the fire by interrupting the chemical reaction and/or removing heat from the fire triangle.Clean agent extinguishers are effective on Class A, B and C fires. 

• Dry Chemical Fire Extinguishers

Dry chemical fire extinguishers extinguish the fire primarily by interrupting the chemical reaction of the fire triangle.

The most widely used type of fire extinguisher is the multipurpose dry chemical that is effective on Class A, B, and C fires. This agent also works by creating a barrier between the oxygen element and the fuel element on Class A fires.

Ordinary dry chemical is for Class B and C fires only. It is important to use the correct extinguisher for the type of fuel! Using the incorrect agent can allow the fire to re-ignite after apparently being extinguished successfully. 

• Wet Chemical Fire Extinguishers

Wet chemical is an agent that extinguishes the fire by removing the heat of the fire triangle and prevents reignition by creating a barrier between the oxygen and fuel elements.

Wet chemical or Class K extinguishers were developed for modern, high efficiency deep fat fryers in commercial cooking operations. Some may also be used on Class A fires in commercial kitchens. 

• Cartridge Operated Dry Chemical Fire Extinguishers

Cartridge operated dry chemical fire extinguishers extinguish the fire primarily by interrupting the chemical reaction of the fire triangle.

Like the stored pressure dry chemical extinguishers, the multipurpose dry chemical is effective on Class A, B and C fires. This agent also works by creating a barrier between the oxygen element and the fuel element on Class A fires.

Ordinary dry chemical is for Class B and C fires only. It is important to use the correct extinguisher for the type of fuel! Using the incorrect agent can allow the fire to reignite after apparently being extinguished successfully. 

• Demonstration on How to Use a Fire Instinguisher

Figure 2 Demonstration on How to Use the Fire Instinguisher

Figure 3 Demonstration on How to Use the Fire Instinguisher