Firefighting - Use of Water

Use of Water

Often, the main way to extinguish a fire is to spray with water. The water has two roles:

• in contact with the fire, it vaporizes, and this vapour displaces the oxygen (the volume of water vapour is 1,700 times greater than liquid water, at 1,000°F (540°C) this expansion is over 4,000 times); leaving the fire with insufficient combustive agent to continue, and it dies out.
• the vaporization of water absorbs the heat; it cools the smoke, air, walls, objects in the room, etc., that could act as further fuel, and thus prevents one of the means that fires grow, which is by "jumping" to nearby heat/fuel sources to start new fires, which then combine.

The extinguishment is thus a combination of "asphyxia" and cooling. The flame itself is suppressed by asphyxia, but the cooling is the most important element to master a fire in a closed area.

Water may be accessed from a pressurized fire hydrant, pumped from water sources such as lakes or rivers, delivered by tanker truck, or dropped from aircraft tankers in fighting forest fires.