Water extinguishers primarily work by cooling the fire. Water has an extreme cooling effect.
The Cooling Mechanism
When a water extinguisher is used, it discharges a stream of water onto the burning material. This water absorbs heat from the fire. When it is directed at flames, it lowers the overall temperature, making it impossible for the fire to burn.
Think of the fire triangle: Fuel, Oxygen, and Heat. Removing or reducing any of these elements can extinguish a fire. Water extinguishers specifically target the 'Heat' element. By significantly reducing the temperature of the burning material and the surrounding area, the fire can no longer sustain the chemical reaction needed to burn.
Why Cooling is Effective
- Heat Absorption: Water requires a lot of heat to turn into steam. This process absorbs a significant amount of energy (heat) from the fire.
- Temperature Reduction: As the water absorbs heat, it directly lowers the temperature of the fuel below its ignition point.
This cooling action is highly effective on Class A fires, which involve ordinary combustible materials like wood, paper, textiles, and rubbish.
Practical Use
Water extinguishers are easily identifiable, typically featuring a bright red body and a red label indicating "Water". They are common in buildings that primarily contain ordinary combustible materials.
Key Points for Usage:
- Always ensure the fire is a Class A fire before using a water extinguisher. Using water on electrical fires (Class C) or flammable liquids/gases (Class B) can be dangerous.
- Aim the nozzle at the base of the fire, sweeping back and forth.
- Do not use on grease fires (Class K) as it can spread the fire.
Understanding the basic principle – that water cools the fire to extinguish it – is key to knowing when and how to use this type of extinguisher effectively and safely.
