Certain
high hazards cannot be controlled or extinguished with ordinary
sprinkler systems, but with water spray systems (also say deluge
systems). They are typical used in high hazard applications where the
need to discharge large quantities of water on the areas of fire.
What
is firefighting foam?
Simply
stated, firefighting foam is a stable mass of small, air-filled bubbles
with a lower density than
oil, gasoline, or water. Foam is made up of three
ingredients…water, a foam concentrate, and
air. Water is mixed with a foam concentrate (proportioned)
to form a foam solution. This solution
is then mixed with air (aspirated) to produce
a foam which readily flows over fuel surfaces.
How do foam agents
work?
Firefighting
foam agents suppress fire by
separating
the fuel from the air (oxygen).
Depending
upon the type of foam agent, this is
done in several ways:
Foam
blankets the fuel surface, smothering
the fire and
separating the flames from the
fuel
surface. The fuel is
cooled by the water content of the
foam.
The
foam blanket suppresses the release of flammable
vapors that can mix with air.