How can we Control Fire?

We know that there are 3 necessary conditions for combustion -

• Fuel
  Presence of Fuel (Combustible Substance)
• Air
  Presence of Air to supply oxygen
• Heat
  Presence of Heat to reach ignition temperature

Thus,

Fire is controlled/stopped by stopping one of 3 conditions of fire

• Remove Fuel
  Example - If some place has caught fire, we should remove nearby kept substances which can catch fire like Petrol, Diesel, LPG, Wood

• Cutoff Air (Removing Supply of Oxygen)
  Example - Use of Fire Extinguisher ,Baking Soda etc to supply Carbon Dioxide .This reduces oxygen supply and fire is stopped

• Remove the heat
  Example - When some object catches fire,we pour water on it.This reduces the temperature  of object below ignition temperature and fire is stopped             

Use of Water

Pouring Water removes fire by 2 methods

• It reduces temperature of substance below ignition temperature
• When water is poured in sufficient quantity,it cuts supply of oxygen which removes fire

Note-

Water works only when things like wood or paper are on fire

It is not used when

• Electrical equipment is on fire as water is good conductor of electricity, and it may cause electric strokes to people who are putting out the fire
• Fires involve oil and petrol - It is because water is heavier than oil,so it sinks below the oil, and oil keeps on burning on the top

 

Use of Fire Extinguisher

Fire Extinguisher contains Carbon Dioxide gas

Carbon Dioxide is heavier than oxygen

When it is sprayed, it covers object like a blanket and cuts oxygen supply

Use of Baking Soda(Sodium Bicarbonate) and Potassium Bicarbonate

Near fire,  these chemicals also provide Carbon Dioxide which reduce oxygen supply

Carbon Dioxide is heavier than oxygen

When it is sprayed,it covers object like a blanket and cuts oxygen supply

Other methods

Some other methods can also be used like-

• Throwing sand or soil over small fires - it cuts off air supply and the fire gets extinguished
• Cooking oil fire can be extinguished by covering the pan with damp cloth - The damp (or wet) cloth cuts off air supply in the cooking oil and the fire gets extinguished
• If a person is caught in fire, use a blanket to cover them - it cuts off air supply and the fire gets extinguished