Class “A” Foam 101 Webcast Questions & Answers

Jeff Cotner responds to participants’ questions from his December 2007 webcast, “Class A Foam 101: Structural Firefighting.”

From the pump operations e-Newsletter, sponsored by

Q. Chief says that the foam is bad for the tank and the tank had to be cleaned by the manufacturer of the engine.

A. That could have been the case. Putting foam in the tank should be a last resort. If you do, the tank must be flushed until you get clean water with no bubbles. Some unapproved concentrates can be corrosive.

Q. How effective is Class “A” foam on a tire fire (piles of shredded tires)?

A. Real time application and tests have shown Class “A” foam to be very effective on tire fires.

Q. Can you store Class “A” foam in a separate foam tank on the apparatus, or will it break down as with batching?

A. Most of your foam engines have a separate tank for the foam. It is an airtight tank with a spring valve that opens when the foam is being used. As long as it is stored in an airtight container and not mixed with water, it will last several years. As long as it is not mixed with water, it will not biodegrade.

Q. When using foam application for structural firefighting, will the hoseline dissipate heat as well as a regular charged “water” hose line?

A. From my personal use and the tests that have been completed, the Class “A” foam is much more effective than plain water.

Q. Do you use compressed air foam system (CAFS) in structural firefighting as first attack, considering flashover?

A. In our operation, if it’s on fire, we use CAFS. If the room is hot enough that we are worried about flashover, we shouldn’t be there.

Q. What do recent studies show with regard to Class “A” and “B” foams masking accelerant detection in the investigations phase?

A. To the best of my knowledge and the information from the lab at the Ohio Fire Marshals Office, the Class “A” foam will mix with the hydrocarbon, but testing will show the presence of it. The Class “B” foam will not do anything to the hydrocarbon. Therefore this should not be a problem.

Q. Have there been any studies yet as to how the foam reacts with ignitable liquids? As a fire investigator, how will it affect my ability to get a positive sample? And how do you defend the effects of a positive sample in court during an arson trial?

A. To the best of my knowledge and the information from the lab at the Ohio Fire Marshals Office, the use of Class “A” foam will not interfere with the lab samples. If you have used Class “A” foam, you should inform the lab you are using for the testing.

Q. What consistency should CAFS foam be–milk-like?

A. If your CAFS is like milk, my guess is you don’t have enough air mixing with the foam solution. That seems to be a problem when pump operators pull the water solution valve all the way open. With the valve open all the way, there is no room for air in the hose. It may depend on your nozzle, too. If you are using a combination fog nozzle, it will always be milky, because the fog nozzle strips the air back out of the stream.

Q. Does the biodegradability break down in the tank or 55-gallon drum?

A. This happens in the tank when mixed with water at normal atmospheric pressure. In the airtight 55-gallon drum, the foam concentrate should not biodegrade at all.

Q. If the discharge handle is all the way out, I still see an increase in stream reach and hear a difference in the sound, but you say I am not getting any air. Please explain.

A. I’m not sure what kind of a system you have, but typically most systems are designed for the discharge handle to be pulled out only so far. Some even have the handles marked for this reason. If you have a hose full of water, there is less room for air. Decreasing the amount of water in the hose allows more room for the air. Your typical CAFS line is going to flow 70 gpm to 120 gpm of water depending on your ratio.

Q. Is there a concern with lower gpms in CAFS applications than traditional gpm recommendations with standard water applications?

A. Keeping the gpm the same as for water rate would be fine, but the application time will be much less. The concern would be that not enough water is being put on the fire. That’s why we use the 1-to- or 2-to-1 ratio of foam solution to air. You always want to have equal to or more water than air. The Class “A” foam makes the water more effective, with some textbooks saying four times more effective than plain water.

Q. Can you please provide a bit more information on your experience of pump-discharge pressure for CAFS operations with handlines? You mentioned in your presentation using 90 pounds per square inch (psi) discharge pressure. Does this need to be adjusted for shorter or longer handline lengths?

A. No, there is not enough friction loss to worry about. That psi can be different per your hose size. We are used to 1¾- and two-inch hose. Any CAFS line with a psi much over 100 is very difficult to handle and can be a safety issue.

Q. Can you mix Phos-Chek foam with National foam?

A. As long as the foam has been tested by the U.S. Forest Service, it is all compatible. The foam bucket will have the “????” stamp on the bucket if it has been tested.

Q. How much time do you have to get your tank cleaned out?

A. It will take two or three weeks before it starts to biodegrade and you will be able to smell it when it happens.

Q. Will foam affect your pump packing, or should you have mechanical seals?

A. No, either will be fine. Most Class “A” foam systems add the foam on the discharge side of the pump. Class “A” foam is a natural degreaser and it would take a strong concentrate of raw concentrate to cause any damage.

Q. Do you know of any testing of CAFS on interior attacks? It seems all of the photos and studies seem to focus on an exterior attack.

A. I don’t know of any studies that focused on interior attack. From personal experience, I can tell you that CAFS is very effective on interior attack. The studies also show that CAFS is very effective on an exterior attack.

Q. Are there any schools in the United States that comprehensively cover all aspects of CAFS?

A. The class at the Ohio Fire Academy covers CAFS in great depth, and I believe Texas AM may be doing some research and testing with Class “A” foam.

Q. Does this mean that there’s a maximum of 250 feet of hose length for 1½-inch hose?

A. No, there is not enough friction loss to worry about hose length.

Q. Does Class “A” foam make a difference when you encounter a Class “D” fire in the steering column of a car?

A. No, the foam still has water. It is going to react the same as water.

Q. Do you have any experience you can share regarding smaller self-contained systems used in smaller incidents like vehicle fires? Possibly compare these systems to larger CAFS or other foam applications.

A. Those systems are very nice for what they are intended to do. The typical setup would be on a rescue or medic. They are different from the bigger systems with an air compressor, because they are limited to the air in the bottle. They typically have 30- to 50-gallon water tanks and enough stored air to make CAFS for that amount of water. They are ideally meant for a car fire or protection at an auto accident with a working extrication. These systems are not intended for structure fire attack.

Q. What is the CAFS setting with the discharge rod all the way open. 1:1, 2:1 as a default setting? It is my understanding that with the rod all the way out, it was 2:1 (2 gpm to 1 CFM) and you were able to dry it from there?

A. That may be true in your system. All seem to be a little different. I have seen systems with the discharge all the way open, the CFM meter is at 0. When you start to close the discharge, you can watch the CFM come up and GPM go down.

Q. What does Class “A” application do when it comes to fire investigation after the fire is extinguished?

A. The most common complaint seems to be that you have to wait for the bubbles to dissipate before you can see anything. But overall, most investigators like it because everything is still there in place. We didn’t use 10,000 gallons of water and flush everything out on the sidewalk or in the basement.

Q. What about the failure of the CAFS hose in Germany?

A. I read the article about that incident, and that’s all the information I have on it. But the hose was a single-jacket hoseline and was exposed to high heat conditions.

Q. We used Class “A” foam to fight a fire of large bales of recycled paper in a large recycle paper warehouse. The first time we used it, we did not have good results. In review, the sprinklers in the warehouse were activated and flowing at the time of application and washed the foam down. We now turn off the sprinklers when we begin applying foam and are having much better success. Have you seen any incidence like this with sprinklers?

A. Any plain water line used in the same area as Class “A” foam will reduce the effectiveness of the foam.

Q. Are the same fire control techniques such as the combination attack as effective with Class “A” foam?

A. Any foam application will be more effective than plain water. Foam application will be more effective with a smooth bore nozzle or combination nozzle on straight stream. CAFS should be used with a smooth bore nozzle for the best results.

Q. What foam classes are best for handling accidents involving hybrid vehicles using hybrid fuels (ethanol) or duel fuels (electric/gasoline)?

A. A plain ethanol fire can be extinguished only with alcohol-type foam. With the E-85 fuels and the small amount of fuel involved with a car fire, Class “A” foam may be effective. If you know going into the event that the fuel tank is ruptured and it is a hybrid car, attacking with an alcohol-type foam may be the best solution.

Q. What is your experience with air entrainment with CAFS versus air entrainment from a fog nozzle? Does an exterior attack “push” fire?

A. CAFS is going to be your best foam option. CAFS or any foam run through a fog nozzle will produce a milk-like foam. This milky foam is not your best foam choice.

As far as pushing fire, any attack will push fire to some extent. A CAFS attack with a smooth bore nozzle has the ability to overrun the push because of the ability to absorb more heat.

Q. Would foam be a good choice for a car fire in a parking garage, as opposed to a car fire on the side of the road?

A. In either case, Class “A” foam will be more effective than water.

Q. What is the “through-the-pump” foam system?

A. In such a system, the foam concentrate is passing through the pump. There are only two styles of systems that do that. One is a suction-side eductor; the other is around the pump.

Jeff Cotner, a 23-year veteran of the fire service, has served the past 16 years with the Bloom Township (OH) Fire Department, where he is a lieutenant. He is vice president of the Ohio Society of Fire Service Instructors and a fire training officer II at the Ohio Fire Academy.

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