COMBUSTION AND FLAME | Class 8 Science Notes

How Do We Control Fire?

Fire control is crucial to prevent accidents and damage in homes, shops, factories, and forests. The first step in case of fire is to call the fire service, whose contact numbers should be known to everyone. Firefighters use water under pressure to extinguish fires by cooling the combustible material below its ignition temperature and cutting off the air supply. Fire requires three essentials: fuel, air (oxygen), and heat (to raise temperature above ignition temperature). Removing any one of these can control fire. Water is the most common fire extinguisher but is effective only for fires involving wood, paper, and similar materials. Water is unsuitable for electrical fires because it conducts electricity and can cause harm. It is also ineffective for oil and petrol fires because water sinks below oil, allowing the oil to continue burning. For electrical and inflammable material fires, carbon dioxide (CO₂) is preferred. CO₂ is heavier than oxygen and blankets the fire, cutting off oxygen supply. It is stored as a liquid under high pressure in cylinders and expands rapidly when released, cooling the fire and lowering the temperature of the fuel. Dry powders like sodium bicarbonate or potassium bicarbonate also release CO₂ near fires, helping extinguish them. The section highlights the importance of understanding the nature of the fire to choose the correct extinguishing method.

📊 Diagram: Fig. 4.6: Firemen extinguish the fire by throwing water under pressure; Fig. 4.7: Fire extinguisher

🔗 Connection: Understanding fire control leads to exploring different types of combustion and flames.