Low expansion foam is the typical application used by municipal fire departments. It can be applied via an air aspirating or non-air aspirating nozzle and can be applied at more standard nozzle pressures such as 100 psi, but can also be applied at even lower nozzle pressures. The expansion ratio will be affected at these lower pressures though. The reason for this lower expansion ratio is there is less pressure (or energy) to create the agitation necessary to mix the foam solution with the air.
Nevertheless, foams that create an aqueous film can be applied successfully on hydrocarbon spills and fires. These foam blankets will not last as long as a thicker and richer foam blanket, such as one applied at a higher ratio, but it will offer the knockdown power that can be the difference between a major incident or a more mundane one.
As with all of the tools we rely on in the fire service, there are advantages and disadvantages of low expansion foam. Until next time, take a look at your department and see if you can answer these questions: " What are your eductors rated at? " What nozzle pressures do your fog nozzles operate at? Are they automatic nozzles or of an adjustable gallonage type? " Do you have any special purpose air-aspirating foam attachments that clip on to your fog nozzles? Do you know how they work? " What are the application rates for the foam concentrates your department uses? You may have to consult the various manufacturers' websites for the specifics, but now is the time to find out!
ARMAND F. GUZZI JR. has been a member of the fire service since 1987. He is a career fire lieutenant with the City of Long Branch, NJ, Fire Department and is the deputy director of the Monmouth County, NJ, Fire Academy where he has taught for over 20 years. He has a masters degree in management and undergraduate degrees in fire science, education, and business administration. View all of Armand's articles here. He can be reached via e-mail firstname.lastname@example.org or email@example.com.