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Which of the following gases is used in fire extinguishers?
Carbon dioxide
Oxygen
Nitrogen
Hydrogen
Carbon dioxide
Carbon dioxide (CO2тАЛ) is widely used in fire extinguishers because it is non-combustible and effectively displaces oxygen, which is necessary for combustion. It is stored under high pressure in liquid form, which expands into a gas upon release, rapidly cooling the area and blanketing the fuel source.
Carbon dioxide (CO2тАЛ) is widely used in fire extinguishers because it is non-combustible and effectively displaces oxygen, which is necessary for combustion. It is stored under high pressure in liquid form, which expands into a gas upon release, rapidly cooling the area and blanketing the fuel source.
Think of it like putting a heavy, fireproof blanket over a campfire; just as the blanket blocks the wind (oxygen) from reaching the logs, the CO2тАЛ gas creates an invisible shield that starves the fire.
CO2 = Cut Off Oxygen = 2 (to the power of) No Fire
C+O2тАЛтЖТCO2тАЛ тАФ The combustion process that fire extinguishers aim to inhibit by displacing O2тАЛ
PV=nRT тАФ The Ideal Gas Law, representing the pressure-volume relationship inside the cylinder
The principle is based on the Fire Triangle: Fuel, Heat, and Oxygen. CO2тАЛ acts by displacing the oxygen around the fire (smothering) and creating a cooling effect due to rapid adiabatic expansion. Because CO2тАЛ is denser than air, it settles over the flame to prevent further ignition.
Carbon dioxide is non-conductive, making it safe for electrical fires.
It leaves no residue after use, unlike water or foam extinguishers.
It is ineffective against metal fires or chemicals that release their own oxygen.
Does not damage electrical equipment
Leaves no chemical residue
Non-corrosive
Risk of frostbite due to cold discharge
Ineffective in high-wind environments
Potential for re-ignition if the heat source remains
Electrical control panels
Laboratory chemical fires
Server rooms
Carbon dioxide is about 1.5 times denser than air.
Option B (Oxygen) supports combustion, so it would intensify the fire.
Option C (Nitrogen) is inert but less dense than CO2тАЛ and harder to store effectively for portable fire suppression.
Option D (Hydrogen) is highly flammable and would cause an explosion.
A is correct тАФ Carbon dioxide acts as a fire suppressant by displacing oxygen and removing the support for the combustion reaction.
Always remember the Fire Triangle: If you remove any one of the three componentsтАФFuel, Heat, or OxygenтАФthe fire will be extinguished.
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