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SECTION 4. CAFS NOZZLE / FLOW RATE / HOSE
COMBINATIONS
A. Nozzles
Compressed air foam can be discharged through various types and sizes of nozzles. Fog nozzles
break down the bubble structure of the foam. This results in "wetter" or reduced expansion foam. The
preferred way to make foam is utilizing smooth bore nozzles with a given hose diameter, smaller tips
will discharge "wetter" foam.
B. Foam Concentrate Ratios
Proportioner settings of 0.2% and 0.6% are typically adequate to produce compressed air foam that is
formed in a hose line and used on Class A combustibles. Higher settings will result in "drier" appearing
foam. Lower settings may result in "slug flow" or discharge pulsation caused by insufficient foam
concentrate in solution to form foam in the hose line.
For Class B or other type foam ratio settings, follow the instructions provided by the foam concentrate
manufacturer.
C. Hose
Utilize fire hose that is rated by the hose manufacturer for use with CAFS. Since the foam is formed
during its transition through the hose line, it is important to utilize the minimum recommended hose
lengths, unless a static mixer is utilized. There is significantly less friction and head loss with
compressed air foam as compared to water or foam solution. Hence, effective fire streams can be
achieved with longer hose lays. Refer to the section, "Suggested Guidelines for the Production of Mid-
Range Compressed Air Foam".
NOTE: Compressed air foam systems have the ability to produce foam of shaving cream consistency.
This type of foam is typically suited for defensive operations such as exposure protection,
barriers or fuels pretreatment. While this type of foam is highly stable and possesses a long
drain time, it is essential to ensure that the foam will release sufficient water to extinguish a fire
in a direct attack situation.
F-1031, Section 2416
Page 11 of 23
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