Constructing fireline with high-expansion foam

Chief Charles Scripps of Painted Rocks Fire and Rescue in Darby, Montana conducted what they call a “foam experiment”. Here is their description of the video:

We flowed foam using a Chemguard foam generator to see if it would have value in the wildland environment. We used 1000 gallons of water with a 2% foam solution (Hale digital foam system). The test took about ten minutes. The foam line was about 1000-1200 feet, 20-40 feet wide and 2-4 feet deep. Further testing for ‘foam and roll’ as well as different percents of foam will take place.


I have seen photos of this procedure before, and it has been used on prescribed fires, but has anyone ever seen it used on a wildfire?

In order to do this, you need a high-expansion foam generator, as opposed to a much smaller medium-expansion foam nozzle which is about 8-12 inches in diameter. Some high-expansion foam generators are so large they are mounted in the back of a pickup truck and most use either a water motor or a gasoline engine to drive a fan, which introduces a large quantity of air into the water/foam solution.

Thanks Chief Scripps and The Latest.


UPDATE September 15, 2009

From The Latest, we have more information from Chief Scripps:

The unit is a Chemguard model 300WP. This is a water driven unit so the engine does not need extra equipment. There are units that are electric or gas driven but neither develops the rpms of the Pok water motor.

I chose this one as it weighs 115 lbs and the next size up weighs 225 lbs. There is a limit to what I can get old volunteers to load, unload and carry safely. The foam was Silvex at 2% as measured by a Hale digital unit. The engine holds 1000 gallons so that was the limit of the trial. The factory recommendation is to run it at 80 psi. So for our first test that’s what we did.

I had seen the YouTube videos of high expansion foam filling aircraft hangers. What intrigued me was when they opened the hanger doors and the foam flowed out on the apron. I wanted to see how it would flow down a mountain. It seems to do this very well. High expansion foam lacks the durability of the denser stuff but it makes a very fast wetline. I think it would be excellent for ‘foam and roll’ in low fuels. I am trying to engineer a method to mount it to my engine so it would function off either side. One of the difficulties for testing is we are running out of summer weather so testing in hot weather conditions is getting difficult.

This is the engine we used.



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Wildfire Today is pleased to welcome a new sponsor, Thermo-Gel.  Chances are you are familiar with their most well-known product, the long lasting gel that can be applied to vertical and horizontal surfaces.  But they also have a more conventional Class A foam, Thermo-Foam.  Both of these have been tested and approved by the U.S. Forest Service.  But I will let them further describe their products:

Thermo-Gel® is a Class “A” fire retardant that is highly effective in fighting wildland and urban interface fires.  The product can also be used for prescribed burns, aviation applications and in the protection of all types of structures from homes to commercial and industrial investments.

We also have a Class A water based foam, Thermo-FoamTM. Thermo-Foam is cost effective and compatible with other Class A foam concentrates.

One more item in our companies’ arsenal of products is our water driven proportioner called Firedos®. It operates without the use of electricity and will proportion all types of Class A and Class B foam and gel.

Check out their web site at  They help to keep Wildfire Today up and running.

Probe: Did Class B foam contaminate water?

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Health officials in Minnesota are trying to determine the scope of water contamination caused by Class B firefighting foam manufactured by 3M. The foam, which 3M stopped making in 2000, contained a family of compounds known as perfluorochemicals which was found in the drinking water in Oakdale and Lake Elmo in 2004 at levels that exceed state health guidelines. These compounds do not break down in the environment and can accumulate in humans and wildlife. The water in 15 other Minnesota cities will be tested in the near future.

When 3M stopped the production of their Class B foam in 2000 they had 50% of the market share. Their announcement sent shock waves throughout the fire community with fire chiefs wondering, 1) what they would use for foam, 2) if they should use ANY foam, and 3) where they stood with respect to the possible harmful effects, if any, on their firefighters and the public.

Here is an excerpt from the announcement that was part of a very interesting article in the May-June 2000 issue of Fireworld:

ST. PAUL, Minnesota—May 16–3M today announced it is phasing out of the perfluorooctanyl chemistry used to produce certain repellents and surfactant products. The affected product lines represent about two percent of 3M’s nearly $16 billion in annual sales. These include Scotchgard products, such as soil, oil and water repellent products; coatings used for oil and grease resistance on paper packaging; fire-fighting foams; and specialty components of other products.

Class B foam is designed to be used on flammable liquid fires and was developed by 3M with the U.S. Navy in the 1960s. It covers burning petroleum with a thin film which smothers the fire.

Many wildland and structure fire organizations use Class A foam on vegetation and structure fires. Class A foam has not been identified in the probe of contaminated water in Minnesota.

The U.S. Forest Service tests and approves the Class A foam that is used by the federal land management agencies. One of the specifications they test for is the biodegradability. Foam concentrates must be “biodegradable” or “readily biodegradable”. Other characteristics they test for include mammalian toxicity, fish toxicity, flash point, fire point, physical properties, exposure protection, corrosion, and surface tension. The Material Safety Data Sheets (MSDS) are listed HERE.

In the late 1970s when I worked for the U.S. Forest Service in California we occasionally used Class B foam on vehicle fires and even some wildland fires, especially on deep-seated fires such as hay stacks or deep duff. But when Class A foam became available we switched completely over, using Class A foam on vehicle and wildland fires.

Some of the early Class B foam was known as “protein foam”. Conventional wisdom was that it was made from fish guts, and that’s what it smelled like. NASTY stuff. Somehow I doubt if that crap contained the perfluorochemicals that 3M later used.

Even though in 2000 3M stopped making the foam currently being investigated, many fire departments probably still have 5-gallon pails of the stuff stored at their fire houses. In 2000 National Foam, Ansul, Chemguard and Angus pointed out that their foam products contained no PFOS and that electro-fluroination which produces the perfluorochemicals is unique to 3M.

More information about the contaminated water is at the Star Tribune.

Alarm company technician accidently fills hangar with foam

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This is not the Long Beach incident, but is a December 11, 2008 photo from a test of a fire suppression foam system at a new aircraft hangar in Salina, Kansas. The system put three feet of foam on the floor in 52 seconds.

An alarm company technician working on an aircraft hanger door at the Long Beach, California airport accidentally triggered the high-expansion foam system, filling the hangar with foam to a depth of six feet. A police helicopter, a police car, and other vehicles were buried in the stuff. Here is a video showing the aftermath.

(the video is no longer available)

HERE is a link to a video shot from the interior of a hangar in Las Vegas during a scheduled test of a similar system.

By the way, in 2006 the Department of Agriculture approved the use of firefighting foam to kill commercial chickens infected with the deadly bird flu virus. In 2002 and 2003 some of our wildland firefighters and incident management teams were used to kill chickens that were infected with Exotic Newcastle Disease using more hands-on methods.