To cut off the supply of air (oxygen) to the fire.
Explanation
Combustion is a chemical reaction that requires three essential components to sustain: fuel, heat (to reach ignition temperature), and an oxidizer (oxygen). This concept is often represented as the "Fire Triangle." Removing any one of these three components results in the extinction of the fire.
Option Analysis:
- To reduce the ignition temperature of the clothes. is Incorrect: Ignition temperature is the minimum temperature at which a substance catches fire. It is an intrinsic physical property of the material (clothes) and cannot be altered by wrapping a blanket.
- To cut off the supply of air (oxygen) to the fire. is Correct: Wrapping a blanket around a person whose clothes are on fire creates a physical barrier between the burning material and the surrounding air. This action cuts off the supply of oxygen, which is necessary for combustion. Without oxygen, the fire cannot sustain itself and is extinguished. This process is technically known as "smothering."
- To absorb the heat generated by the fire. is Incorrect: While a blanket may absorb some heat, its primary and immediate function in extinguishing the fire is not heat absorption. In fact, a blanket acts as an insulator and might initially trap heat, but the lack of oxygen stops the generation of new heat.
- To prevent the person from running and spreading the fire. is Incorrect: While preventing a person from running is important to stop the fire from flaring up due to increased air circulation, the scientific reason for using a blanket specifically is to block the air supply, not merely to restrain the individual.
Key Takeaway:
The primary scientific principle behind using a blanket to extinguish fire on a person is smothering, which breaks the Fire Triangle by cutting off the supply of oxygen.