Fire extinguisher and its working mechanism

  • A fire extinguisher is a protective device which is red in color and is used to extinguish fire.
  • Red is the color associated with both danger and fire and hence metallic cases in fire extinguishers are colored red.
  • Secondly,it is most easy to see red, especially in a darker environment, such as a smoke-filled room.
  • Metallic vessel in a fire extinguisher contains sodium bicarbonate solution and a small bottle of concentrated sulfuric acid.

Working mechanism of a fire extinguisher:

  • All fire extinguishers work on the basic principle of removing any of the three basic elements needed for combustion—oxygen, heat or fuel.
  • Carbon dioxide is a gas which is neither combustible nor a supporter of combustion.
  • When we need carbon dioxide gas to extinguish fire, the vessel is inverted.
  • Once the vessel is inverted, the bottle of concentrated sulfuric acid strikes against the floor which makes the plug of the acid containing bottle fall down.

  • Due to this, the acid comes in contact with sodium bicarbonate solution and react together giving carbon dioxide gas.

2NaHCO3 + H2SO4 (conc.) ———–> Na2SO4 + 2H2O + 2CO2

  • The gas produced in the above reaction comes out through the nozzle with high pressure and puts off fire making a blanket like covering over the surface of the flame.
  • The blanket like covering prevents the oxygen from coming in contact with the fire and extinguishes the fire.

Fire extinguisher and its working mechanism