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There are a variety of effective fire fighting foams in use. These are made from liquid concentrates
and are referred to as mechanical or air foam. The first fire fighting foams were chemical foams made
from powders and are now considered obsolete.
Types of Foam
Foams are identified by the base materials used in their formulation or by the
characteristics of the expanded form. Examples are protein, fluoroprotein, aqueous film forming
foam and high expansion. The latter two indicate characteristics rather than materials.
Foam Concentrates
The standard foam concentrates are intended for use primarily on hydrocarbon
fires. Water soluble liquids will destroy foam made from these concentrates. Therefore, special
concentrates are needed for use on flammables such as alcohol and other polar solvents. These
concentrates are generally referred to as alcohol resistant concentrates. There are also special
concentrates designed for low temperature storage which remain fluid enough for proper proportioning
down to -20 deg. F. The standard compounds are not damaged by freezing, but they obviously must be
in a liquid state to be used.
Foam Solution
Foam solution is formed by proportioning the proper amount of concentrate into a
water stream in the piping system. These solutions contain 1% to 6% concentrate depending on the
type used. Some systems use premixed solutions stored in a tank. Any type of water may be used;
fresh, hard, soft, or salt, as long as it does not contain contaminants such as oil that would
affect foam quality. If there is any question as to the suitability of the water, it should be
tested.
Mechanical Foam
All foams are formed by the agitation of a solution of the foam concentrate and
water in the presence of air, thus the general designation mechanical foam or air foam. The term
air foam, or just foam, is generally used in referring to this agent.
Foam Quality
The quality of the expanded foam is dependent to a large extent on the concentrate.
However, good or poor foam can be made from the same concentrate depending on the foam making
equipment used. Therefore, it is important that the equipment be properly matched with the concentrate.
Expansion Ratios
Foams are further identified by the expansion that takes place when the solution
is aerated. Generally, expansions up to 20 are called low expansion, 20 to 200 are called medium
expansion, and 200 and above are high expansion. Low expansion foams, such as AFFF, are highly mobile
providing rapid coverage and excellent area protection. On the other hand, high expansion foam is
primarily used for total flooding applications of enclosed spaces based upon volume coverage. When
selecting a foam for a particular hazard, it is important to know the characteristics the foam should
have to provide the best protection for that hazard.
Fire Prevention
As well as being an extinguishing agent for flammable liquid fires, foam is also
useful to prevent fire by covering, or blanketing, flammable liquid spills before they become ignited.
(AFFF) Aqueous Film-Forming Foam
A synthetic foam consisting of fluorochemical and hydrocarbon
surfactants solvents and water with the ability to spread on a hydrocarbon fuel.
Alcohol Resistant Type AFFF
Concentrates also contain a polymer which produces a protective membrane
between the foam and the water soluble fuel.
 Dry Chemical Systems
Foam Protection
Gaseous Systems
Pilotex® Ultra High Speed Deluge System
Water Spray Systems
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Fire
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