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Fluorine Free and AFFF – what changes

What is different from AFFF to fluorine free foam (F3)?

While all AFFF’s use essentially the same technology (some use it better than others) and were considered functionally similar, this is not true for F3 foams. It will probably take quite a few years (probably decades) for the new technologies to mature to the same point.

F3 foams are free of persistent fluorosurfactants and siloxanes. This is their one major benefit. Despite any marketing hype, I haven’t seen data that shows one area where they fight hydrocarbon fires better than AFFF or fluoroprotein foams do. In some cases they can provide similar performance, at least in small scale testing. This will hopefully change as they mature, but right now that is the reality.

Alcohol Resistant F3 foams (AR-F3) appear to have reasonable performance on some polar solvents, but for others their performance is very poor, they are not consistent. Much of the fire fighting ability does not rely on the aqueous film and it is possible that there is benefit from the fluorinated surfactant for simple polar solvents such as ethanol and methanol.

The short term environmental impact of F3 foams can be worse than that of AFFF’s, the total organic load can be quite a lot higher.  This is much less of a concern than persistence, but it is a concern if the run-off can reach water bodies quickly.

The main things we lose when changing to F3 foams are:-

  • The aqueous film. This feature improved the knock down time for spill fires. It may also lubricate foam flow over the fuel in other applications as well. It helped with vapour sealing if correctly formulated (having an aqueous film doesn’t automatically mean it is effective at vapour sealing film).
  • Fuel shedding. Superficially this seems like the most important feature of fluorosurfactant technology, but over-shadowed by the more novel aqueous film in popular thought. After more researching, there doesn’t seem to be a lot of experimental support for the concept of fuel spreading. I suspect that there is a different mechanism involved, and not one that F3 foam can easily duplicate.
  • The low viscosity additives for AR-AFFF are probably not fluorine free. So low viscosity AR F3 foams are probably not possible at present.

If new technologies can recreate the aqueous film (silicone – siloxane surfactants can but are also persistent chemicals, so not viable alternatives) that alone will not make them full fluorosurfactant replacements. There is some process that enables AFFF’s to work well when applied forcefully. This should be the most important area for development.

When evaluating F3 foams for various applications, they need to do more than extinguish fires at the normal foam system design application rates. The design rates specified in standards have a safety factor built in. Usually in the order of 60% over the proven extinguishing rate.

AFFF can extinguish fires at application rates below 2.4 lpm/sqm at large scale, F3 foams need to be proven at this level also.

Beware of product demonstration videos. One video I have seen purports to demonstrate a capability similar to AFFF but the actual application rate used was about 2.5 times the normal AFFF design application rate. Product demonstration tests ARE NOT engineering data, they mean nothing unless the testing is soundly engineered, documented and peer reviewed. I have yet to see a foam product video that contains useful fire protection engineering information.


Extinguishment and Burnback Tests of Fluorinated and Fluorine-free Firefighting Foams with and without Film Formation.  Suppression, Detection and Signaling Research and Applications – A Technical Working Conference
(SUPDET 2011) 22-25 March 2011 Orlando, FL  Bradley Williams,  Timothy Murray,  Christopher Butterworth,  Zachary Burger, Ronald Sheinson,  James Fleming,  Clarence Whitehurst,  and John Farley