Legacy firefighting foams (i.e., aqueous film-forming foam [AFFF]) used by the Department of Defense (DoD) and the civil aviation community are facing increasing regulatory scrutiny throughout the world due to both environmental and human health concerns associated with fluorinated surfactants. In December 2019, Congress passed the FY20 National Defense Authorization Act (NDAA), which prohibited uncontrolled release of AFFF at military installations. The NDAA also required the development of a new foam specification to aid in the phase-out of per- and polyfluoroalkyl substances-containing AFFF at all land-based military installations by 2024.

Five SERDP & ESTCP programs were conducted over the past four years to develop the firefighting performance metrics for the new fluorine-free foam (F3), military specification (MIL-PRF-32725). During the initial program, a detailed literature search was conducted to identify the commercially available products. Over sixty products were identified as being marketed as “environmentally friendly” AFFF alternatives. Twenty-five of them were selected and tested against approval scale fires (i.e., 28ft² pan fires conducted with gasoline and Jet A). During these screening tests, five products demonstrated superior firefighting capabilities and were selected for further evaluation. During a follow-on effort, these products were tested against all the requirements (physical and chemical properties, and fire performance tests) in the legacy AFFF military specification (MIL-PRF-24385). Although not as good as the legacy AFFFs, the leading F3s performed very well during the smaller scale assessments but the testing was not representative of actual fire scenarios/incidents. Prior to publishing MIL-PRF-32725, the capabilities and limitations of the leading F3s needed to be validated against representative, real-scale fire scenarios.

The validation tests summarized in the project Final Report were conducted over a two-year period using the facilities and fire scenarios that were the basis for the development of AFFF. The test parameters were selected to represent shore-based aircraft rescue and fire-fighting (ARFF) applications (i.e., foam solutions were made with freshwater and the fires were produced using kerosene-based aviation fuels). The fires included extremely large uncontained fuel spill fires and obstructed running fuel fire scenarios.

The validation tests were conducted at the Naval Air Warfare Center Weapons Division at China Lake, CA over a two-year period and consisted of four phases.

1. The Phase I tests were conducted in May 2021 and included manual firefighting using a standard fire hose equipped with a 125 gallon per minute (gpm) vari-nozzle (and other nozzle configurations).
2. The Phase II tests were conducted in October 2021 and included combatting the fires using a turret installed on a small ARFF vehicle. The fire sizes were scaled up by a factor of two to maintain an application rate of 0.05 gpm/ft² between the two phases (i.e., foam solution flow rate divided by the fuel surface area).
3. The Phase III tests were conducted in May 2022 and included an assessment of novel nozzle designs specifically suited to discharge F3s (i.e., variable aspiration, better pattern control) and the development of better application techniques and firefighting tactics/doctrine to improve the capabilities of the F3s.
4. The Phase IV tests were conducted in October 2022 and included a final validation of the leading F3 products using the optimal techniques developed during the previous phase. The Fire and Emergency Services Working Group was invited to witness the final phase of validation testing and participate in the development and the refinement of training materials required to effectively field the new F3s throughout the various DoD facilities. Fires included extremely large uncontained fuel spill fires and obstructed running fuel fire scenarios.

These tests were the final needed step prior to publishing the MIL-PRF-32725 in January of 2023.

Approximately 150 validation tests and demonstrations were conducted during the four phases of this program (108 hose line tests and 44 turret tests). On completion of the four phases of validation testing, the extinguishment times of the F3 products had been consistently reduced to about 1.5 times (i.e., 1.5 times being the worst-case) longer than AFFF but this delta was measured in seconds. Specifically, the spill fire extinguishment times for AFFF were between 40-50 seconds (i.e., 45 seconds using the hose line and 50 seconds using the turret) while the F3 extinguishment times were about 50 seconds for the hose line and about 70 seconds using the turret. The running fuel fires were typically extinguished using AFFF in less than 60 seconds and in about 90 seconds using the F3s.

With respect to foam application techniques and firefighting tactics, the same techniques worked well for both AFFF and F3s; however, the F3s required more finesse when applying the foam to the fuel surface (i.e., to minimize the forceful application of the foam onto the fuel surface). This needs to be emphasized during training and when using these products during actual incidents/events. The hardware, tactics and techniques that were developed to optimize the capabilities of the F3s also tended to increase AFFF performance (but to a lesser degree). 

Upon completion of these final validation tests, the test team and the various DoD organizations involved in the testing were convinced that these leading F3 products could be used to effectively protect liquid fuel fire hazards throughout DoD land-based applications (with a very limited number of exceptions). These tests were the final step needed prior to publishing the MIL-PRF-32725 in January of 2023.

DISTRIBUTION STATEMENT A. Approved for public release: distribution unlimited.

WP21-3461