New foam concentrates, new flammable liquid hazards and new foam proportioning systems have altered the look of municipal foam firefighting. Here are some recent changes.

Within the past decade, manufacturers have introduced a variety of new foam concentrates that can do more with less. Class A foams that used to be applied at a standard 1% now can handle many structure and vegetation firefighting duties at concentrations as low as 0.1%. And although many Class B foams are still proportioned at 3% or 6% for flammable liquid fires, other formulations can now do the job at ratios of only 1% or 3%.

The effect on municipal apparatus design has been significant. Pumpers equipped with 10-gallon Class A foam cells now can now deliver up to 5,000 gallons of finished foam at 0.2% or 2,000 gallons of foam at 0.5%. At those ratios, Class A foam becomes an attractive means of attack for all structure and wildland fires, whether it is delivered as nozzle-aspirated foam or compressed-air foam.

Likewise with 10-gallon Class B foam cells, pumpers can deliver up to 1,000 gallon of finished foam at 1% to handle fires that might have required three times as much concentrate in the past. More importantly, budget-conscious departments that might not have had any Class B foam capability, can now produce up to 500 gallons with a single can of concentrate and a simple foam eductor or self-educting nozzle.

New foam concentrates arrived just in time to handle a shift in the types of flammable liquid fires faced by many departments. Within the last few years, many states have introduced ethanol-blended fuels for motor vehicles to reduce the country's dependency on foreign oil. These fuels mix ethanol, also known as ethyl alcohol, with gasoline or diesel in ratios as high as 85% ethanol for some gasoline blends. The ethanol is derived from corn, sugar or other agricultural products and is often produced in the vicinity of the source, sometimes in plants along railroad sidings or highways adjacent to the fields. From there, the ethanol is transported directly to fuel distribution terminals around the country and is blended at the loading rack as tank trucks are being filled.

The combination of the new fuel formulations and the new locations where the ethanol is blended with the gasoline or diesel presents two new firefighting hazards. First, alcohol fires require special extinguishing agents; alcohol-resistant aqueous film-forming foams are the most common. Traditional methods of fire suppression involving water fog sprays or regular foams may work on very small fires involving alcohol, but they will not work on more substantial fires. Second, many rural departments may be unaware of the fact that ethanol plants or blended-fuel distribution points are within their jurisdictions. In some cases, these departments may be unprepared to respond and may unknowingly place their personnel in danger by using inappropriate methods or extinguishing agents.

Fortunately, there are new AR-AFFF concentrates that can be mixed in ratios as low as 3% for alcohol fires, rather than the old 6% ratios. These foams let even small departments handle blended-fuel fires without carrying a large amount of concentrate on their apparatus. For safety, some departments have switched to alcohol-resistant foams for all flammable liquid fires in areas where blended motor fuels are sold.

Foam-proportioning systems also have changed over the years. Older models that could only deliver foam at one or two fixed ratios within a narrow range have been replaced by new models that allow continuous selection of ratios across a broad range.

For departments that use foam regularly, some advanced systems now sense flow rates, temperatures, and other factors, which are fed continuously to a microprocessor controller to accurately deliver the optimal amount of foam under varying conditions. Not only do these systems deliver the proper foam ratios for each firefighting situation, but they can help conserve foam and reduce operating costs.

For departments that rarely use foam, but still want to have the capability to handle specific hazards, eductors and pressurized bladder systems have been upgraded to let users select ratios for many types of foams. These compact, low-cost units have the additional advantages of requiring no electrical power and very little maintenance, which makes them a popular choice for small departments.

The next generation of Class B foam systems may involve low flow rates and high pressures. A series of designs currently under development with the U.S. Air Force use ultra-high-pressure foam to quickly suppress flammable liquid fires. The smallest system is designed to be mounted on lightweight, four-wheel all-terrain vehicles for deployment at forward combat bases. It delivers foam through handlines at 14 gpm and 1,200 psi and is already seeing service in Iraq to fight fuel fires. Subsequent systems increased the flow to 100 gpm, and the final step is predicted to be in the 300-gpm range.

Tests of the ultra-high-pressure system show that suppression can be achieved with about one-half the flow rate and one-third the agent of current foam systems. Horizontal reach is comparable to existing systems. Several manufacturers worked with the Air Force to develop pumps, nozzles, monitors, and other components for the prototype systems, which remain under evaluation.