Water

The Best-Known Extinguishing Agent

General Principle of Extinction

When exposed to heat, water turns into steam. The resulting water vapor displaces air (steam occupies 1,700 times the volume of liquid water at 100 °C, and up to 4,200 times at 650 °C), depriving the fire of oxygen.

Water acts through two complementary mechanisms:

• Cooling: Water absorbs a large amount of heat as it heats up and vaporizes, lowering the temperature of flames, smoke, and surfaces, thereby preventing the fire from spreading.

• Smothering: As it turns into steam, water expands up to 4,200 times its original volume, displacing air and lowering the oxygen concentration around the fire.

 

Applications

Water is ideal for Class A fires involving solid materials.

For other types of fires, water may need to be combined with additives or used in a different form (such as water mist) to enhance its extinguishing performance.

In high-risk or particularly harsh environments, the use of a foam additive is necessary—this corresponds to foam suppression systems.