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Thread: Class A/B Foam How Effective

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    Default Class A/B Foam How Effective

    We will be taking delivery on a new Pierce Rescue Engine later this year and the unit will have 750 gallons of water with a 50 gallon foam tank with a Husky 12 Foam System, no CAFS. About 90% of our first due is without hydrants.The question we have is should we place Class A for structural fire suppression or Class B for petroleum/solvent fire suppression on this unit? My solution is to use a combination ClassA/B Foam similar to a product under the name of F-500 Encapsulator.
    Our first due is mostly rural/suburban residential, (suburb of Baltimore),6-8 farms/barns,limited commercial structures, no interstate highways, we do have a small airport that handles single engine planes only although it is not an active airport. Most of our fire fighting is single family dwellings and an occasional auto fire. Does anyone have any experience with a combination Class A/B Foam?


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    I would run strictly one or the other. Does your truck have the ability to run an external foam eductor or an ez fill system?
    I would recommend that you run the foam you would use most often and I bet that would be class A foam for structure fires. If you happened upon the low % chance of a chemical fire and needed class B, you could then flush/switch over for that specific scenario. With the external eductor, you can drop that into a foam reservoir (foam bucket or even a portable tank) and feed foam that way.

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    What we do is run one type of foam in the truck tank, then have a foam pro-pak with the other type on the truck, that way we have both types available.

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    Quote Originally Posted by 93Cobra View Post
    I would run strictly one or the other. Does your truck have the ability to run an external foam eductor or an ez fill system?
    I would recommend that you run the foam you would use most often and I bet that would be class A foam for structure fires. If you happened upon the low % chance of a chemical fire and needed class B, you could then flush/switch over for that specific scenario. With the external eductor, you can drop that into a foam reservoir (foam bucket or even a portable tank) and feed foam that way.
    Yes we have an external eductor.

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    Have you looked at F-500 or Fireade as an alternative? We have a similiar issue and went with class A foam. We carry B foam in 5 gallon buckets. We have used the A foam quite a bit and are very happy with the foam system. Unfortunately, we have had 3-4 car fires in the last couple of months that have required B foam. We are testing F-500 now as a catch all type product. We are still going to carry our B foam but the F-500 seems to be working out well.

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    We carry Williams Thunderstorm 1 x 3 foam in BOTH our class A tank and class B tank. We meter it done to .1 or .3 percent for use in 'class A' fires and have seen very good results from it.

    One thing to consider is that a lot of what would be considered 'class A' applications have a lot of class B products burning. The amount of plastics and synthetics burning in or on structures is very significant today.

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    With the proportioning rates of the Class B foam, 50 gallons won't go very far...

    I often run into this with customers who want A and B foam tanks on a new engine. The amount of foam you'd need to carry for a decent size Class B fire is pretty substantial.
    "Share your knowledge - it's a way to achieve immortality." - Stolen from Chase Sargent's Buddy to Boss program

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    Quote Originally Posted by chief60 View Post
    Have you looked at F-500 or Fireade as an alternative? We have a similiar issue and went with class A foam. We carry B foam in 5 gallon buckets. We have used the A foam quite a bit and are very happy with the foam system. Unfortunately, we have had 3-4 car fires in the last couple of months that have required B foam. We are testing F-500 now as a catch all type product. We are still going to carry our B foam but the F-500 seems to be working out well.
    We are considering F-500 as a catch all, my personal feeling on catch all's is that they are most likely adaquate but not great at what they are intended to do. It would be nice to get some feedback from someone who has recent first hand experience with this type of foam.

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    Quote Originally Posted by npfd801 View Post
    With the proportioning rates of the Class B foam, 50 gallons won't go very far...

    I often run into this with customers who want A and B foam tanks on a new engine. The amount of foam you'd need to carry for a decent size Class B fire is pretty substantial.
    Next due company carries 100-150 gallons of Class B on one of their rigs.

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    Quote Originally Posted by RE33 View Post
    We carry Williams Thunderstorm 1 x 3 foam in BOTH our class A tank and class B tank. We meter it done to .1 or .3 percent for use in 'class A' fires and have seen very good results from it.

    One thing to consider is that a lot of what would be considered 'class A' applications have a lot of class B products burning. The amount of plastics and synthetics burning in or on structures is very significant today.
    Is Williams Thunderstorm 1x3 a combination A/B Foam?

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    Class A foam is primarily a surfactant, which is to say that it breaks down the surface tension of water. In addition, the portion of the foam concentrate molecule that repels other water in order to break the surface tension is also attracted to carbon. The result is that when you apply finished class A foam to a dense carbon based fuel (like wood) the water is broken down into much smaller micro droplets that absorb much more quickly into the fuel.

    Class B foam works differently as it changes the specific gravity of the water to make it lighter than liquid hydrocarbon fuels, and further it works to bind the water together in order to create a self healing blanket to smother vapors and keep them from escaping the pool of flammable liquid.

    If you look at what class A and class B foams are supposed to do to water you will quickly realize that any foam claiming to do both is likely to perform poorly. The two purposes are diametrically opposed to one another. In other words: a jack of all trades is a master of none.
    Just a guy...

    Lieutenant - Woodbury, MN FD (Retired)
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    Disclaimer: The facts and opinions expressed above are mine, and mine alone, and are not intended to represent the views of any company I have ever worked for, past or present.

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    Johngagemn,

    I couldn't have said it any better..........And agree 100% with you

    Be safe,

    Capt Lou
    "GotFoam?"
    Last edited by CaptLou; 08-15-2010 at 10:11 PM.

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    As previously stated, If you are looking to have class B foam capability, using a 1 x 3 AR-AFFF would be the best way to go, as most of them can be used at low percentages on class A fires (.1 - 1%). The down sides I can think of are more system maintenance, more expensve foam and in most cases a limited ability to handle any "decent" sized B fire. Another factor to take into account is that AR foams are more viscous and injection foam systems have limitations on their ability to handle these fluids. I always consider the amount of B foam carried on most engines enough to put out a gasoline tank fire from a typical car fire, however, it will go MUCH further on A fires.

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    Seems that we should be hearing more about this type of product. The company trying to sell us states that this is a new product, then you go to their website and they have testimonials dating bact to 1999 so it isn't so new. Is the reason we don't hear more about this is because it really does not work as well as they say or is it they don't have good representation to sell this?
    Like anything I am sure it has its limitations. Is it the cost?

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    We have been using it at my volunteer department for several years and have had great success. It only recently became UL rated. We replaced both our Class A & B foam with this product.
    The cost is between A and B. I think about $25\gal. We run it at .4% for house\building fires. Awesome in a pressure can.

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    Snakeoil

    See discussion by Johngagemn

    As noted above you can successfully use Cl B (as Ar-Afff) at low % on for class A. IF your foam pump can handle the viscosity of the stuff. And it's a bit expensive compared to any Cl A. Something to be said for only carrying one type of foam. Note that Chemguard has a new low viscosity 1x3 Ar-Afff that nearly all foam pumps can handle as 1800cps.

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    You may be able to achieve a faster knockdown on a class A fire using a class B foam than you would with plain water, this is because if you are truly flowing foam bubbles then you have expanded the surface area of the water which means you will absorb BTUs of heat faster than you would with larger solid drops of water. I stress the word MAY because with a lot of B foams you may not be making good foam at the lower percentages typically flowed in a class A application.

    All that said, unless a foam concentrate actually functions as a surfactant, it is NOT a true class A foam, and will not give you the benefits of faster water absorption into class A fuels such as wood, paper, rubber, etc. A foams are also designed specifically to foam appropriately at lower percentages (typically 0.2-0.3% for CAFS applications and 0.5% for aspirated foam applications).

    The problem lies with the fact that there is no current standard that tests the effectiveness of what people are claiming to work as a class A foam. There are some very good foams out there, there are a bunch that are OK, and then there is some real junk too. Best to make sure that what you are putting through your handlines is actually designed to do what you need it to do rather than hoping/trusting that something is a magic bullet. When you talk to the sales people who are trying to sell you foam don't be afraid to ask questions, or put more simply: buyer beware, folks.

    Stay safe out there...
    Just a guy...

    Lieutenant - Woodbury, MN FD (Retired)
    Road Captain - Red Knights MC, MN4

    Disclaimer: The facts and opinions expressed above are mine, and mine alone, and are not intended to represent the views of any company I have ever worked for, past or present.

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    Quote Originally Posted by neiowa View Post
    Snakeoil

    See discussion by Johngagemn

    As noted above you can successfully use Cl B (as Ar-Afff) at low % on for class A. IF your foam pump can handle the viscosity of the stuff. And it's a bit expensive compared to any Cl A. Something to be said for only carrying one type of foam. Note that Chemguard has a new low viscosity 1x3 Ar-Afff that nearly all foam pumps can handle as 1800cps.
    Could you elaborate of that comment. We have been using FireAide since 2006 and have used it on both structure fires and liquid fire and have not had any problems. What are we missing?

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    Default getasupply

    Quote Originally Posted by Johngagemn View Post
    Class A foam is primarily a surfactant, which is to say that it breaks down the surface tension of water. In addition, the portion of the foam concentrate molecule that repels other water in order to break the surface tension is also attracted to carbon. The result is that when you apply finished class A foam to a dense carbon based fuel (like wood) the water is broken down into much smaller micro droplets that absorb much more quickly into the fuel.

    Class B foam works differently as it changes the specific gravity of the water to make it lighter than liquid hydrocarbon fuels, and further it works to bind the water together in order to create a self healing blanket to smother vapors and keep them from escaping the pool of flammable liquid.

    If you look at what class A and class B foams are supposed to do to water you will quickly realize that any foam claiming to do both is likely to perform poorly. The two purposes are diametrically opposed to one another. In other words: a jack of all trades is a master of none.
    I really like what you have said here, please let me add some thoughts from the foam classes I have taught we carry class B to put on a spill to prevent fire. To fight a B fire requires a lot of concentration and a lot of concentrate.

    Class A foam I love it, we use it from the get go on any fire. we only use the b on spills to prevent a fire.

    Combination juice over priced, undertested and not UL approved

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