Question

Explain foam-type fire extinguisher and its uses.

Answer 1

• Foam-type extinguishers are the most effective and safe extinguisher to use on fire involving flammable liquids and solid combustible.
• It is consist of a metallic cylinder which consists of a knob and a nozzle tube.
• The cylinder is filled with a solution of saturated $\mathrm{Sodium}\mathrm{bicarbonate}\left({\mathrm{NaHCO}}_3\right)$.
• A glass bottle containing $\mathrm{Aluminium}\mathrm{sulphate}$ is also kept inside the metallic cylinder. Whenever we strike the knob against a hard surface, the glass bottle breaks down and $\mathrm{Aluminium}\mathrm{sulphate}$ is come to contact with saturated solution of $\mathrm{Sodium}\mathrm{bicarbonate}\left({\mathrm{NaHCO}}_3\right)$ and it reacts to produce$\mathrm{Carbon}\mathrm{dioxide}\left({\mathrm{CO}}_2\right)$.
• We know that $\mathrm{Carbon}\mathrm{dioxide}\left({\mathrm{CO}}_2\right)$ is neither burns nor supports combustion.
• A substance known as saponin is added to the saturated solution of $\mathrm{Sodium}\mathrm{bicarbonate}\left({\mathrm{NaHCO}}_3\right)$ to produce the foam of $\mathrm{Carbon}\mathrm{dioxide}\left({\mathrm{CO}}_2\right)$.The foam then comes through the nozzle and is directed towards the fire.

Uses:Foam-type extinguisher is used to extinguish fire caused by electrical and inflammable liquids like petrol and kerosene.