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:
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.