Departments that are considering speccing a compressed-air foam system on their next apparatus may want to ask about a few things that might turn a good cafs unit into a great one.

There are several major manufacturers of CAF systems, each with its own subtleties, but the basic principle of every CAF system is the same. Every unit mixes water with foam concentrate to create a foam solution; air is then injected into the foam solution to create the finished foam. However, each of the three major components of caf systems — water, foam and air — have issues that should be considered before making a purchase.

Water works

Typically the water system consists of a standard fire pump that receives water from an onboard tank, positive-pressure source or draft. Departments that routinely see high-intake pressures may have some difficulties in creating high volumes of compressed air due to the pumping engine not turning at an increased rpm. A low engine rpm typically reduces the compressor’s ability to generate the high volumes of air needed for compressed-air foam.

One possible solution for this problem is gating the intake. Many departments have used this method to control intake pressures, even if they don’t have a caf system; however, this can be labor-intensive because the pump operator must continually monitor the intake and discharge pressure and make adjustments as flow rates change.