Classification of fire extinguishers

Fires can be defined as the presence of fire in an unwanted location. They are capable of causing, in addition to material damage, falls, burns and smoke poisoning.

Fire, in turn, is the result of a chemical chain reaction, and for this reaction to occur, the following are necessary:
• Oxidizable material (fuel);
• Oxidizing material (oxidizing);
• Ignition source (energy) and
• Chain reaction.
- Fuel is the oxidizable material (solid, liquid or gaseous) capable of reacting with the oxidizer in a combustion reaction;
- Oxidant is the gaseous material (usually oxygen) that can react with a fuel, thus producing combustion;
- Ignition is the agent that starts the combustion process, it is the minimum initial energy required introduced into the fuel/oxidizer mixture;
- Chain reaction is the process of combustion sustainability, due to the presence of free radicals that are formed during the fuel burning process.
It is extremely important to know and identify well the fire to be fought, before choosing the extinguishing agent (fire fighting equipment). A mistake in choosing a fire extinguisher can render the effort to fight the flames useless, and may even make the situation worse: increase or spread the flames further, or create new causes of fire (short circuits).

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The main types of fire extinguishers are as follows:
1. Fire extinguisher H2O: water in liquid form (jet or mist);
2. Foam-based fire extinguisher: mechanical foam;
3. Extinguisher for Inert Gases and Vapors: carbon dioxide (CO2), Nitrogen, Water Vapor;

4. Chemical powder fire extinguisher: sodium bicarbonate.
Fire classes:
THE - Solid fibrous materials, such as: wood, paper, fabric, etc. which are characterized by leaving, after burning, residues such as coal and ash. This class of fire must be fought with H fire extinguishers.2O or Foam;
B - Flammable liquids and gases, or solids that liquefy to ignite: gasoline, LPG, paraffin, etc. In this case NO water-based fire extinguishers can be used;
Ç - Energized electrical equipment: motors, generators, cables, etc. Chemical powder and Gas extinguishers are allowed for this type of fire.
By Líria Alves
Graduated in Chemistry

Source: Brazil School -

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