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Class A foam vs. 3% AFFF - effectiveness??

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  • Class A foam vs. 3% AFFF - effectiveness??

    Still learning the best uses of Class A foam with a new FoamPro system. Foam can get to be expensive. Was given some 3%AFFF foam. If I dilute the 3% to 1%, will it be as effective as Class A? I think not, but before I look a gift horse in the mouth, what do the panel of Firehouse experts assembled here today think??

    Remember, it IS as bad as you think and they ARE out to get you!

  • #2
    Hi Jim,

    The AFFF is exactly what it is, AFFF or Class "B" foam. It is not Class "A" foam, regardless if you dilute the Class "B" or not. Each type of foam is design for a specific application. Class "A" was designed for and works best on ordinary combustibles. REMEMBER, NEVER EVER MIX CLASS "A" AND "B" FOAMS TOGETHER IN YOUR TANK OR SYSTEM!!!!!!! THEY DO NOT LIKR EACH OTHER! IT WILL TURN THE CONTENTS OF YOUR TANK TO "JELLO" AS WELL AS ALL OF THE PLUMBING AND THE PUMP, IF IT GETS THAT FAR.
    Hope this helps.

    Capt. Lou
    "Got Foam"


    • #3
      Lou brings up a good point. Don't put the B in your tank! They don't like to mix, and cleaning it will be a mess.

      Also, Class A foams where designed to be more environmentally friendly -- they break down easier, and while they still shouldn't be discharged into catch basins/ponds/streams/wetlands, they won't do a lot of damage.

      Class B foams usually last longer in the environment and have more significant environmental impacts.

      With either, it's recommended you practice where the foam is allowed evaporate. Class A in a waterway will stick around for awhile before it leaves the ecosystem; Class B could very well cause a fish kill or similiar problem if it gets into a waterway.


      • #4
        Yes I agree foam (class-A) can get expensive. We have been using it for structure fires only. The cars and dumpsters or any other small outside type fires have straight water put to them. If there are exposures involved then we may use it for quicker knockdown but it is a judgement call for us in that situation. We have not had the opportunity to use any of the class-B foam yet, but we sure go through the class-A.

        [This message has been edited by ffnbs (edited 06-07-2001).]


        • #5
          Danger Danger Warning Warning! Not all foams are equal.

          Some of the Class "A" foams have alcohol in the formulation. Do not mix!

          Be careful of the "A" "B" systems when you are using a AR type foam and a Class "A" foams that contain alcohols.

          One big costly mess!

          Never mix two type of foams in a storage tank or container even if they are both the same type. i.e. AFFF & AFFF or FFFP & FFFP. Each manufacturer has their own formulations and some foams do not like each other when mixed.

          AFFF will not act like a Class "A" in your Foam Pro. The viscosity is different between the two.

          Wanta do training? Cut the Class "A" concentrate 4 to 1 for non-fire training projects, works great for this and saves you money.


          • #6
            Thanks for all the excellent information.


            • #7
              Class A and B foams are 2 different animals all together.

              Class A is Carbon loving
              Class B is Carbon repelling.

              Class A foam due to the design of the molecule will draw into a carbon based product in short it is absorbed.

              Class B is repelled by carbon it floats away. Thus the aquiouos layer.

              Smoke obsurations tests done by the US military show these factors.

              In a live burn test a class A fog was applied at 40% visablity, in 30 seconds the visablity improved to 80% and with in 60 Seconds to 94%. Class A is carbon loving and will bond with the airborne carbons and bring them to the ground.

              Class B was also applied in the same sinario.
              at 40% visablity a B fog was introduced. at 30 seconds visablity improved to around 50% at 60 seconds recduced to 20% then continued to near 0 visablity. Class B repells carbon and is not abosorbed by the carbon product. I will suffocate the fuel but as there is no wetting abiltiy the fuel is not cooled and has a high potential for reingnition.

              Same as the reason you cant us Class A on a liquid hydrocarbon fuel. The Class a will be drwan into the liquid fuel. There is no vapor suppresion after a very short time.

              Sorry for the spelling. Spell check is non functional


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