Due to environmental and health concerns over per- and polyfluoroalkyl substances (PFASs) in aqueous film forming foams (AFFFs) being used at U.S. airports, the FAA is seeking a suitable replacement. The FAA evaluated commercially available fluorine-free foams (FFFs), which do not contain PFASs, to determine if any FFF can be considered a suitable replacement for AFFF for use on aviation fuel fires.
FFFs were tested to the Military Specification MIL-PRF-24385F and International Civil Aviation Organization (ICAO) Doc 9137-AN/989 Airport Services Manual, Part 1: Rescue and Fire Fighting Level C standards for extinguishment time, burnback resistance, foamability, drain down time, storage stability, physical properties, chemical properties and toxicity. The results were compared against the current AFFF performance under the same test standards. Additional live fire tests with modified test parameters, such as fuel type, application method, and preburn duration, were also conducted to further quantify the higher performing FFF candidates’ performances as compared to AFFF and how these parameters affect test results.
None of the FFFs evaluated had an equivalent extinguishing performance to AFFF. While other performance metrics or physical characteristics can be met or surpassed, the primary metric of concern is the extinguishment performance of the foam. In all the nominal concentration gasoline fires, none of the FFFs evaluated were able to extinguish the fire in an equal or lesser amount of time. Of all the Jet-A test fires, only one of the scenarios, the ICAO test fire, resulted in extinguishment times of a FFF that surpassed the performance of AFFFs consistently, with both foams achieving extinguishment well after the foam application had been completed. All the other Jet-A fuel fire scenarios resulted in extinguishment times of FFF candidates significantly slower than AFFF. Overall, none of the FFF candidates consistently had equivalent or comparable extinguishing performance. One candidate FFF did have significantly greater burnback protection than AFFF while the remaining FFF candidates’ burnback protections were significantly less. All the tested FFFs exhibited reduced performance with the application of dry chemical. Additionally, surface burning was a commonly observed trait of the FFF candidates that is typically not observed with AFFF.