By Jonathan M. Hinson
Firefighting foam has been around for many years, from the powder foam to protein foam to the synthetic foam in use today.
Originally designed to extinguish simple hydrocarbon-based fuel fires, today’s foams can be used on Class A fires; alcohol-based fuel fires; and, of course, hydrocarbon fuel fires. Technology has advanced to make foam operations more effective, simplistic, and cost-effective. Flammable and combustible liquids are everywhere and being transported through all modes of transportation. Hopefully, all fire departments have enough foam resources readily available to effect a rescue from a flammable liquid incident. Some communities may have a higher risk or threat, so more foam resources are needed. Whether a department has an eductor and three buckets of foam or thousands of gallons of foam with master stream devices, there are still some basic principles and tips that can apply to both situations to facilitate a successful foam operation.
Foam Percentages
Whether using onboard foam systems or portable foam eductors, the proper percentage of foam must be educted into the water stream to combat the problem at hand. The proper percentage depends on the fuel burning and, most importantly, the manufacturer’s recommendations. Class B foam is used at one, three, or six percent, describing the percentage of foam concentrate in the foam solution. The manufacturer through testing has determined at what percentage foam should be used. If the foam is alcohol-resistive, then the recommendations will also cover what percentage is appropriate for both hydrocarbon-based fires and polar solvents.
These recommendations are generally clearly stated in big numbers on the foam’s storage container. Using a percentage less than the recommendation will make the operation ineffective; increasing the percentage can make operations more effective with quicker extinguishment. However, when using a higher percentage, foam system operators must understand that they will use double if not triple the amount of concentrate required, potentially depleting the concentrate supply prematurely.
|
1 Photos by author. |
Class A foams are generally used at 0.1 to 1.0 percent, once again depending on the manufacturer’s recommendations. In most cases, the lower percentages are used for fire attack and extinguishment while the higher end of the range can be used for exposure protection. Using higher than recommended percentages of Class A foam generally does not result in more effective operations like seen with Class B foams.
Use onboard foam systems and eductors to properly mix foam concentrate and water to make foam solution. You must perform this process flawlessly to have a successful foam operation. However, the foam concentrate must be made into finished foam through proper application to have a completely successful foam operation. The foam must be applied continuously and without failures. Proper application is critical with Class B foams, as they make a film or membrane to properly extinguish. Class A is a direct application just like water, so no film or membrane is produced.
Foam Application
The ensuing discussion about foam application applies to Class B foams. In basic training, firefighters are taught to apply foam with three different methods: roll on, bank on, and rain down. Nozzle operators must ensure that the stream is not plunged into the product, causing the foam to be pushed under the product and thus less effec