Fire Extinguisher Classification: Which One to Use Based on the Fire

Fire extinguishers are the most effective means to effectively fight a fire principle since it is essential to intervene immediately, at the latest, within 15-20 minutes from when the combustion has started.

This is why knowing the classification of fire extinguishers can be decisive to identify the most suitable type to be placed in a given environment, in correlation with the nature of the potential fuel. There are different types of fire extinguishers to use, which include foam fire extinguishers, water extinguishers, and carbon dioxide extinguishers.

Classification based on the Extinguishing Agent

A further classification of fire extinguishers is based on the extinguishing agent present inside the tank and, consequently, on the extinguishing capacity of the extinguishers themselves in relation to the classification of fire classes.

Water Extinguisher

The water extinguisher was probably the first portable means designed for extinguishing fires, recently revived by the ecological problems associated with using other chemical compounds.

The tank of this type of fire extinguisher contains about 90% of water, while the rest of the volume is made up of filming agents and additives, which act both by cooling and by extinguishing. It has a permanent pressurization system, and the extinguishing agent is delivered by nebulization to produce greater heat exchange and absorption.

Powder Fire Extinguisher

In this type of fire extinguisher, the tank contains a fire-fighting powder composed of various chemical substances mixed, which can be divided into two macro-categories:

• ABC powder, generally made with ammonium sulphate and phosphate, capable of extinguishing several types of fire (wood, paper, coal, flammable liquids, and gases);
• BC powder, consisting mainly of sodium bicarbonate and specific for fires of flammable liquids and gases.

The chemical powders extinguish the fire by acting as inhibitors of the still unburned material, suffocating the flame and immediately lowering the combustion temperature through an endogenous action.

Halogenated Hydrocarbon Fire Extinguisher

It contains halogenated hydrocarbons as an extinguishing agent, also commonly called Halons, which intervene in the combustion reaction by removing oxygen and consequent extinguishing the fire.

Following the adoption of international protocols aimed at banning the use of ozone-depleting substances harmful to the environment, halons have been replaced by hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs), which have an impoverishment index of the ozone layer close to “0”.

Foam Water Extinguisher

Foam extinguishers are used to extinguish class A and B fires, which occur by suffocation due to the expansion of a layer of foam film on the fire.

They are in turn divided into two sub-categories:

• mechanical foam extinguishers, in which the escape of foaming liquids mixed in water occurs, by compression, through a discharge lance equipped with holes to suck in the air necessary for the expansion of the foam;
• chemical foam fire extinguishers, which exploit the chemical reaction between aluminum sulphate and sodium bicarbonate, which, when mixed at the time of use, develop the carbon dioxide necessary for the product to escape.

Carbon Dioxide Fire Extinguisher

A first fundamental difference compared to other types of fire extinguishers is given by the …