Originally Posted by
Cameronian
Thanks for that information Main Gear Touchdown. If the foam is mixed only with air then what acts to inhibit combustion? I had imagined, with no background in the subject whatsoever, that the foam's main purpose was to hold the carbon dioxide (in the bubbles) on the fire to give it a chance to suppress the flames. If that had been the case then it would have suppressed those poor guys' respiration too!
I have experiance only with AFFF (Aqueous Film Forming Foam) fire extinguishers. But the main aim of AFFF is to smother the fire, therefor taking away the oxygen needed, and starving the fire. It is used primarily on Class A and B fires which includes Papers,fabrics,flammable liquids.
The only real problem with AFFF is that it's cooling properties are not great, and on some occaisions if the AFFF layer is broken, then sufficient heat is there to re-ignite the fire.
The only time Carbon dioxcide would be needed is to pressurise the container, therefor providing a propellent to get the stuff out of the hose on fire extinguishers and portable trolleys.