1953 County Street, East Taunton MA 02718 USA
(800)822-4744 or (508)822-7330 / Email: firstname.lastname@example.org / www.jwfshers.com
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difference of containing tens of thousands of gallons less, which can be a significant savings on the
construction cost of the building.
Foam types are broken into low, medium, and
high expansion, as well as wetting agents. This
refers to how much the foam expands when it is
aerated (air is added):
• Low expansion ratio: 2: 1 to 20: 1.
• Medium expansion ratio: 20: 1 to 200: 1.
• High expansion ratio: >200: 1.
The higher the expansion ratio, the “deeper” the
foam blanket will be. Foam normally generated
from fire apparatus is usually low-expansion foam.
High-expansion foam is normally generated from
large “generators” that look like (and may include)
ventilation fans. Some fire departments have this
equipment, and high-expansion foam has been used
to fight high-piled storage fires, basement fires,
and other incidents where it becomes important
to essentially “engulf” the burning material with a
“wall” of foam.
A foam system generally functions like a regular
sprinkler system except that it has a mechanism to
inject/educt foam into the sprinkler water. Foam
may come from a tank through a variable speed
pump that meters the amount of foam into the
sprinkler water piping depending on
the gpm flow through the piping. This
is typically a closed-head foam-water
In the case of an open-head, deluge
foam-water sprinkler system, there is a
fixed water flow and fixed foam flow that
is created by some of the sprinkler water
being diverted to a tank with a bladder of
foam in it. The water pressure compresses
the bladder, forcing the foam concentrate
out through piping that mixes it with the
sprinkler water flow. The sprinkler nozzles
may or may not be the aerating type, adding air into the discharged foam mixture.
If you are dispatched to a fire, fire
alarm, or foam system discharge at a
facility with a foam system, there are
some important tactics to follow.
First, understand the area to which you
are responding, the hazards in the area, and
how the system is supposed to function.
Second, be prepared to pump the
fire department connection if there is
an actual fire to ensure that the foam
system receives adequate water supply to
function properly. (See “Firefighting in
Sprinklered Buildings,” FireRescue, July
It is very important that you know the proper
pressure to pump to the connection, as many foam
systems have specific parameters to stay within
when pumping the connection that supports
the foam system. The system may not function
if pumped at pressures greater than 125 psi, but
this is something that needs to be evaluated and
preplanned before a fire occurs.
Be aware of the duration for which the foam
supply is designed. Most foam systems have a
Firefighters need to understand
a bit about foam systems so
that they can work with them
effectively during a fire incident
or to minimize any damage
and loss should a system