Class A Foam

Class A Foam is specially formulated to make water more effective for firefighting. The surfactants in Class A foam significantly reduce water’s surface tension and, when mixed with air, create a superior foam blanket that surrounds fuels with a thick foam blanket. This creates a barrier between the fuel and the fire, knocking down the fire faster than water alone, and allowing fire fighters to see the areas of application. Making the water more effective reduces the amount of water needed to extinguish the fire, reduces water damage and increases fire fighter safety through quicker knockdown and reduced mop-up/overhaul requirements.

Starting with our workhorse PHOS-CHEK® WD881, Perimeter Solutions offers a portfolio of Class A Foam products that can suit virtually any Class A application.

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High Performance Class A Foam Concentrate
Economy Class A Foam Concentrate
Economy Class A Foam Concentrate

Class A Foam Benefits:

Industrial Firefighting

Wildland Fire Management:

PHOS-CHEK® WD881 Class A foam has been proven to be a valuable tool to suppress wildland fires when applied from fixed wing airplanes, helicopters equipped with fixed tanks or with slung buckets, from standard fire engines and rapid attack brush trucks, and for use in 5 gallon backpacks.

Since foam stretches water’s firefighting power, it is especially valuable where water availability is critically short. Foam has been shown to reduce the amount of resources and time necessary for mop-up which saves money and improves firefighter safety.

Foam can be used from the ground to reinforce a mineral soil fire line or natural fire barrier. Wildland firefighters can use foam to lay a wet line from which to backfire.

Ground vehicles equipped with Compressed Air Foam Systems have proven valuable to wildland firefighters for protecting structures in advance of wildland fires.

Municipal Fire Departments:

Many municipal fire departments have standard operating procedures that state “Class A foam shall be used in any situation where plain water had previously been indicated as the extinguishing agent”.

  • Structural firefighting: PHOS-CHEK WD881 Class A foam benefits fire departments in several respects. Foam helps achieve faster fire knockdown. This benefit reduces firefighter fatigue and cuts down water damage. PHOS-CHEK foam can help complete overhaul up to three times faster than plain water because it holds water on the fuel longer allowing it to penetrate and soak into the fuels more effectively. Using less water also reduces the chance of ceiling collapse. The ability of fire department companies to quickly return to service is seen as a significant advantage and an improvement in the level of service they can provide.

Protection of structures adjacent to the fire is another case where PHOS-CHEK’s foam blanket is valuable. For vertical exposures, PHOS-CHEK foam will create a thick foam blanket which will reflect radiant heat, allow the exposure to absorb water for prolonged protection and help insulate the surface.

  • Vehicle fires: PHOS-CHEK WD881 Class A foam is also used successfully for vehicle fires. Foam coats and smothers fires in the engine compartment. The penetrating power effectively helps to extinguish fires in the interior compartment where fabric and carpet are involved.
  • Nuisance fires: The same coating and penetrating power of PHOS-CHEK foam is useful to fight fires in garbage dumps, dumpsters, and trash piles. Some of these types of fires often require expensive heavy equipment and take considerable time to pull apart and overhaul when using water alone.
  • Bee attacks: Class A foam has been found to be highly effective in neutralizing attacking bee swarms. The use of PHOS-CHEK WD881 foam allows for water to adhere to the bees better. Wet bees cannot fly. Using Class A foam allows firefighters to knock the bees from the air and off the victim.

Rural Fire Departments:

Rural firefighters, who must carry their own water, especially benefit from the enhanced effectiveness of adding PHOS-CHEK WD881 Class A foam to their water. Field and laboratory tests show that water mixed with only 0.1%-1.0% foam concentrate is often 3 to 5 times more effective than plain water. Therefore, fewer water shuttle trips may be required. Fewer trips save money and reduce equipment maintenance. Improving firefighting efficiency with foam means volunteer firefighters can return to their paid job quicker.

Class A Foam Markets

Tire Fires:

According to the National Fire Protection Association, Class A fuels include materials such as vegetation, wood, cloth paper, some plastics and rubber. Tires are among the toughest fires to extinguish. Water alone on tires simply beads up and rapidly rolls off. The reduced surface tension of PHOS-CHEK Class A foam allows water to sheet out and cover the tire surface and to penetrate deeper into the piles. The foam blanket created with 0.1% to 1.0% foam concentrate builds up a thick layer of water on the tire surface. The more water available, the more heat it can remove from the fire. The longer the water remains on the surface, the more time is available for water to absorb its full heat capacity, thus making it more efficient.

Coal Mine Fires:

PHOS-CHEK foam can be used to extinguish fires in and around coal mining operations. Foam effectively puts out fires in conveyor belts, gearboxes, coalbunkers and tailing piles. Class A foam has also been used on coal seam fires. A foam blanket will keep a thick layer of water on top of the coal which will continue to drip water deep into the pile and helps to smother the fire.

Industrial Fire Fighting:

PHOS-CHEK Class A foam concentrate is an excellent firefighting tool for many industrial applications. Industries that have considerable challenges protecting large quantities of classic Class A fuels include cotton gins and cottonseed oil mills, textile mills, grain elevators, and countless other companies that use paper, fabric, and wood to produce their final products. PHOS-CHEK foam is ideal for wharf and warehouse fires, especially when they contain paper, cotton, or wood products.

Hydrochloric Acid Vapor Suppression:

PHOS-CHEK WD881 Class A foam has been used successfully for vapor suppression of hydrochloric acid (HCL). In 1997, PHOS-CHEK WD881 was used to control vapors for an estimated spill of 1000 and 3000 gallons of 32% concentrated HCL in the San Diego, CA area. A 40:1 air aspirated medium expansion nozzle was used with 0.8% PHOS-CHEK WD881 foam solution. Within a few minutes after initial application, the vapor cloud disappeared. Only 8 gallons of PHOS-CHEK WD881 was used to control vapors of HCL at this incident. Outside third-party testing was conducted by Hughes Associates in 1999 validating the use of PHOS-CHEK WD881 Class A foam for this purpose.


Hazardous materials or nuclear, biological, and chemical incidents often involve civilian, governmental or fire service personnel that have been exposed to potentially deadly chemical agents. The State of California, Office of Emergency Services, student manual entitled “Haz Mat Terrorist Response Counter Terrorist Decon” has identified PHOS-CHEK WD881 Class A foam as an approved method for decontamination. (Ref. Page 15-16 of the document). Many fire departments today are equipped with Class A foam. PHOS-CHEK WD881 Class A foam is a detergent and the surfactants present in the product will help to release the contamination.

Prescribed Burning:

The intentional burning of specified plots of land has many benefits. After harvest, fields that grew cane, rice, wheat, oats and straw, for example, are often burned to clear stubble and debris and for pest control. Grass seed farms routinely use this technique. Logging slash often is burned intentionally to clear land for reforestation. In order to reduce fire hazards, areas of extensive weed growth are reduced by the combination of herbicides and prescribed burning.

PHOS-CHEK WD881 Class A foam is a cost-effective tool to help manage prescribed burns and reduce smoke generation. Foam’s ability to cling and coat grasses, brush, and trees with thick layers of water is useful to build wet lines from which to start a fire; to reinforce control lines, to protect valuable trees bordering the burn site; to protect structures, fences and other resources within the burn; to protect seed trees within the burn; to reduce flame height and rate of spread as fire approaches control lines; to help prevent and control spot fires outside the burn. As in wildland fires, PHOS-CHEK WD881 can significantly reduce mop-up time and resources.