This article is the third of four excerpts from a new book, Class A Foam - Best Practice for Structure Firefighters , by Dominic J. Colletti. Larry Davis is the technical editor of this 240-page educational textbook (© 1998 by Lyon's Publishing, Royersford, PA). Ordering information is available...
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Using no nozzle on an attack hose is tough for structure firefighters to accept. This is understandably so, because in our previous discussion of NAFS, the type and design of each nozzle are very important factors in the quality of the finished foam produced. With CAFS, the hoseline nozzle does not create the finished foam. The CAFS apparatus creates the foam inside its piping and/or the attack hoseline - not at the nozzle! All that is required is a control valve so the hose team can shut off foam flow.
If desired, in place of using only a 1/4-turn ball control valve on a CAFS attack hose, you can attach an appropriate size smooth-bore nozzle to the valve (for example, for a 1 3/4-inch attack hose, use a 1 3/8-inch smoothbore nozzle attached to a 1/4-turn ball valve with the same inside diameter). Adding a smoothbore nozzle to the control valve will not improve stream quality or reach. It will, however, make firefighters "feel better" because there is some sort of nozzle in their hands.
In using CAFS for interior structure firefighting, some departments take issue with using a smoothbore nozzle for fire attack. This is because most have previously trained with and now use fog nozzles on a narrow fog pattern for interior attack with water. In these instances, a less desirable alternative is to install a variable-gallon/constant-flow or fog nozzle adjusted to the "flush" position on the hose in place of the smooth bore nozzle.
Most 1 1/2-inch variable-gallon fog nozzles have manual flow adjustments at 60-, 95-, 125-gpm, and so on. If some manufacturer's nozzles are adjusted further, into the "flush" position, the internal waterway opens up to over 300-gpm. This "flush" opening is large enough to allow a marginal compressed air foam stream through, with breakup of a portion of the finished foam bubble structure.
Even though some variable-gallon nozzles can be operated in the "flush" position as an alternative to a smoothbore nozzle to apply compressed air foam, nevertheless some compressed air foam bubbles are destroyed as they pass through the nozzle reverting to foam solution, reducing foam effectiveness. The only advantage of using the variable-gallon nozzle on "flush" is that the nozzle operator has the option to deliver either a CAFS straight stream or fog pattern for interior attack.
Each department using CAFS must evaluate their nozzle options and identify which works for them. High-quality training is the key to success when implementing the use of CAFS.
CAFS foam consistency is flexible for different tactical firefighting uses. Adjusting the volumes of foam solution and compressed air entering discharge lines alters finished foam product consistency. For example, a low-expansion ratio of air to water of 7:1 forms a quick-draining, runny Class A foam blanket used for quick knockdowns on direct structure attack. A medium expansion ratio of 30:1 produces a dry, shaving cream-like discharge used for exposure protection applications.
Dominic J. Colletti is the national OEM accounts manager at Hale Products Inc. in Conshohocken, PA. Colletti is a volunteer firefighter with the Royersford, PA, Fire Department and has served with Engine Company 3 of the Coram, NY, Fire Department. He has over a decade of experience in the research and development of Class A foam and CAFS application for structure firefighting. His e-mail address is: CafsExpert@aol.com