The Department of Defense’s (DoD) goal is to eliminate per and polyfluoroalkyl substances (PFAS) from firefighting formulations as soon as possible. Towards this end, projects were sought to demonstrate and validate more environmentally sustainable PFAS-free fire suppression alternatives against the current performance requirements outlined in MIL-PRF-24385F (SH) with interim amendment 3 for aqueous film-forming foams (AFFF). The intent of this solicitation was to demonstrate and validate promising PFAS-free firefighting agents against the current military requirements, identify methodologies to more effectively identify promising candidate formulations, and develop training solutions to aid firefighters in use of PFAS-free AFFF. The following considerations were of interest:

• Demonstration and validation of PFAS-free fire AFFF. Due to the expense of large-scale testing, only PFAS-free fire suppression alternatives that demonstrate promise based on initial small-scale testing (28 ft² and 50 ft² tests of the current MILSPEC) are of interest for large scale demonstrations. Information on the historical 1260 ft² pool fire test is available in Section 4.7.7.3 of MIL-F-24385B.
• Demonstration and validation of methods to improve the stability of PFAS-free AFFF concentrate and diluted solution for use. Evidence has shown that some of these formulations may not be fully stable and phase separate, change viscosity prior to use that can affect firefighting performance. Projects that evaluate the stability of formulations as a function of conditions and/or demonstrate methods to increase the stability of PFAS-free AFFF are of interest.
• Testing and evaluation of the compatibility of multiple approved PFAS-free AFFF formulations. Traditional PFAS-containing AFFF formulations from different manufacturers appear to be compatible. Yet, PFAS-free AFFF formulations may not be compatible and mixing with other PFAS-free AFFF formulations is not recommended by the manufacturer. The logistics issues associated with this would increase cost and time associated with AFFF management or require single source purchasing. Thus, MILSPEC testing on mixtures of PFAS-free AFFF is sought to determine whether certain mixtures could be used together or gain understanding of the degree of the compatibility problem. For compatible solutions, the duration of compatibility is also of interest.
• Demonstration and validation of alternative methodologies for quantitatively evaluating the effectiveness of firefighting formulations against realistic DoD threats presented by Class B liquid pool fires. Technologies should be validated against current full-scale qualification tests to show improved repeatability and characterization. This could include objective test methods to measure control, containment, edge effects, and burnback, as well as other relevant performance characteristics (e.g., flickering, flashover, vapor permeability, heat flux, etc.) that can be correlated with extinguishment performance on liquid pool fires using a variety of fuel threats, including jet fuel, gasoline, and other flammable liquids. Proposals may also include testing to correlate existing small-scale test data with larger scale foam performance. Note that there is a related FY24 SERDP SON, Improved Pool Fire Testing for PFAS-Free Firefighting Formulations, and Modernized Training Methodologies for DoD Firefighters. The SERDP SON is focused on hypothesized fire characteristics that are not currently measured or quantified to evaluate fire extinguishment time for AFFF and PFAS-free AFFF. The ESTCP topic is focused on methodologies that have been tested at the small-scale fire testing level and have demonstrated effectiveness in assessment extinguishment time.
• Demonstration and validation of mature firefighting training methodologies to simulate live fire training with foam on liquid pool fires. Training methodologies should reflect realistic threats in DoD relevant environments, while reducing or eliminating air and water emissions and hazardous waste generation from training activities. Note that there is a related FY24 SERDP SON, Improved Pool Fire Testing for PFAS-Free Firefighting Formulations, and Modernized Training Methodologies for DoD Firefighters. The SERDP SON is focused on hypothesized, unproven firefighting training methods and laboratory experiments to test these the hypothesized methods. The ESTCP topic is focused on methodologies that have been tested for at least small-scale fire tests and have demonstrated effective simulation of real firefighting scenarios.

The materials and processes to be demonstrated/validated should already be developed to at least a Technology Readiness Level (TRL) of 4, and the proposed project should bring them to TRL 7 or higher. Alternative formulations should be production-level materials rather than laboratory-scale samples. Projects must demonstrate producibility, defined as the ability to be produced in the near term to meet the current DoD airfield or shipboard use requirement.

Field testing in military relevant environments should have been included in the proposed project. Alternative formulations must be compatible with generally used storage equipment (e.g., polyethylene) and piping (steel, copper-nickel, bronze alloys), while providing comparable corrosion rates to current AFFF. Formulations should meet requirements with fresh and salt water at multiple delivered concentrations. In addition, formulation stability must be demonstrated. Proposals may include approaches to demonstrate similar correlation between large and small scale fire tests with PFAS-free fire suppression alternatives, in lieu of large scale tests.

Proposals should have included an assessment of the human health and environmental impacts of proposed ingredients, formulations, and byproducts if such testing has not already been completed. This should expand on commonly used aquatic toxicity, chemical oxygen demand and biodegradability testing required in the MIL-PRF-24385F. These proposals should establish a baseline lifecycle framework and identify the lifecycle inventory elements currently known, those to be investigated during the project, and those beyond the scope of the proposed work. Any completed testing on human health and environmental impacts of proposed ingredients, formulations, and byproducts should be summarized in the proposal.

All projects must involve at least one DoD organization as a funded co-performer that is considered a stakeholder for the intended application. Proposals should also indicate the involvement of other DoD stakeholders at the consultant level and higher.

AFFF is a water-based foam used by the military since the 1970s for fire suppression in ships, shore fixed systems, aircraft hangars, and to extinguish liquid fuel fires. AFFF mixtures containing significant quantities of perfluorooctane sulfonate (PFOS) and related PFAS compounds were in use until 2002, when production stopped; however, the DoD continued to use PFAS-containing AFFF stocks for some time after the halt in production. It is estimated that there are still over 500,000 gallons of PFAS-based AFFF in stock in the DoD inventory. The Air Force and Navy are the primary users for AFFF, with an estimated current stockpile of 423,000 and 97,000 gallons, respectively.

New AFFF formulations with telomer-based, short-chain fluorosurfactants (C6 or shorter) have been shown to have a reduced environmental impact. However, these materials still have the potential to persist in the environment or even to contain trace quantities of PFOS or perfluorooctanoic acid (PFOA). The 2020 National Defense Authorization Act requires that the DoD publish a new military specification for PFAS-free foam by 31 January 2023 and that PFAS-free foam be available for use by 1 October 2023. In addition, the procurement and use of fluorinated AFFF would be prohibited for land-based fires after 1 October 2023 and 1 October 2024 respectively. As such, the relevant military specification, MIL-PRF-24385F, is being revised to effectively preclude the use of PFAS.

Industry has identified potential PFAS-free alternative foams; however, none of these technologies meet the fire performance or intercompatability required for military applications. MIL-PRF-24385 requires the DoD to evaluate AFFF for foamability and sealability using specific test conditions (nozzles and application rate) to meet specific fire extinguishment and burn back times. Many PFAS-free alternatives can be used to extinguish pool fires, but do not meet the strict requirements outlined in MIL-PRF-24385F (SH) w/ interim amendment 3.

This problem is not unique to military operations. Civil aviation continues to use AFFF or fluorosurfactant-free fire suppression foams that do not meet the performance of AFFF. Alternatives that meet or exceed current AFFF performance requirements without fluorosurfactants would dramatically reduce the environmental impact of fire suppression training and operations while maintaining the safety of personnel at crash sites or around liquid poolfires.

DoD limits live fire training with foam agents (e.g., training with PFAS foams is prohibited) and typically does not train firefighters with liquid pool fires, to reduce release of foam and fuels to the environment. Any foam discharge must be contained and treated as hazardous waste. Typical firefighting training relies on simulated fire scenarios (typically propane burners) that are manually turned off once the instructor determines that an adequate amount of water (not foam) has been applied to the fire. Realistic live-fire training with fielded firefighting agents is vital to maintaining readiness across DoD. PFAS-containing AFFF are very effective in extinguishing fire and enables the firefighters to rapidly apply the AFFF without issues with burnback. Trials so far have shown that firefighters need some time and experience to effectively use the PFAS-free AFFF products to maximize their effectiveness and reduce the chance of injury. As such, the transition to PFAS-free foams requires additional training for nearly every firefighter and first responder across DoD to ensure optimal readiness. The timelines for transition to the PFAS-free formulations are too long to give hands-on real fire-fighting training to each firefighter and first responder. Alternative training methodologies are thus critical to readying these personnel for real firefighting scenarios once PFAS-containing AFFF is no longer used.

Test requirements have been developed and refined over the past four decades based on significant test history (with PFAS-containing foams) that correlates large scale, realistic fire scenarios to performance in the 28 ft² test. PFAS-free foams have different characteristics and material properties that impact their performance in a fire scenario. As a result, new test methodologies and measurements may correlate more strongly with success and failure than current methods. New test methodologies or performance requirements may be incorporated into future specification revisions for both shore- and sea-based applications.