Aqueous film forming foams (AFFF) are required to be phased out at all military sites by October 1, 2024, as directed by the National Defense Authorization Act (NDAA). By January 2023, an updated MIL-SPEC for Class B (flammable liquid) firefighting foam will be established. In the meantime, the NDAA forbids training exercises that release any AFFF. The goal of the Department of Defense is to eliminate all fluorinated compounds from firefighting foam formulations. The objective of this study was to evaluate the effectiveness of various additives in firefighting foam formulations to improve fluorine-free foam (F3) produced by ADA Technologies, Inc. so as to meet current MIL-SPEC standards. The study aimed to determine the impact of these additives on extinguishment time, burn-back time, and other relevant metrics, as well as assess the potential benefits and limitations of using these additives in F3 formulations.

Testing of F3 formulations was conducted using a full strength 3% solution delivered to a live fire in a compressed air foam (CAF) delivery system and a non-aspirated delivery. The smaller 1 ft² tests used a CAF system, while larger tests used the non-aspirated system. Additives tested included carbonates, polymers, and siloxane surfactants. Carbonate and polymer additives were milled into nanoparticles using a rotary mill to enhance their compatibility with the F3 formulations. The resulting nanoparticles were added to the F3 formulations at a concentration of 1%.

A carbonate tested (carbonate 3) improved extinguishment and burnback resistance in the CAF system, but had little to no effect in the non-aspirated system. Polymer additives tested improved extinguishment time and burnback resistance in both systems. However, some polymers (polymer 1) created non-Newtonian fluids, which were not particularly compatible with the non-aspirated nozzle used and hence not tested on the larger 5 ft² and 12.5 ft² tests. Siloxane surfactants improved extinguishment and burnback in both systems but decreased foamability and performed poorly at higher ambient temperatures. Certain formulations containing organosiloxane surfactant agents were observed to display the qualitative presence of an aqueous film over gasoline, this lead to improved extinguishment and burn-back times.

The findings from this study can be used to supplement existing formulations to meet the newly released MIL-SPEC for fluorine free firefighting foam. This project assists in phasing out the use of AFFF that can contain toxic per- and polyfluoroalkyl substances. This will help lead to the development of a high-performance, fluorine-free firefighting foam that is effective for fire suppression while minimizing the potential environmental and health hazards associated with traditional fluorine-containing firefighting foams.