The objectives of this project were to (a) rigorously evaluate commercial off-the-shelf (COTS) and maturing perfluoroalkyl substance (PFAS)-free foams (PFF) (previously referred to as fluorine-free aqueous film-forming foams [fluorine-free AFFF) to determine where they fall short of MIL-PRF-24385F specifications; (b) determine whether commonly available firefighting engineering technology such as compressed air foam (CAF) or ultra-high pressure (UHP) and/or minor chemical modifications will allow the foams to meet the required standards of extinguishment and burnback times; and (c) demonstrate the CAF and UHP technologies at field scale. This project was supplemental to previously completed and reported ESTCP WP19-5299 project.

Several COTS PFF are available, but none of them currently meet the very stringent MIL-PRF-24385F specifications, especially for the extinguishment time (30 seconds maximum), and for some, the burnback time (360 seconds minimum). It is known that extinguishment and burnback times can be altered by affecting the quality of the foam produced. Both CAF and UHP are known to affect foam formation, and by adjusting the amount of air injection, pressure, and flow rates, one can choose the foam quality necessary (balancing spreadability with longevity) to extinguish a fire. PFF modifications can be (1) chemical (i.e., taking dry agents that cannot be used to combat fire alone and combining them with the PFF); or (2) physical (e.g., delivering PFF with UHP systems that can reach higher output pressures than traditional firefighting systems). Additionally, minor issues such as slightly higher than acceptable corrosion rates could be addressed by the manufacturer by simple formula changes, such as adding a corrosion inhibitor. By combining both the engineering and the chemical solutions, it was expected that one or more PFF could be modified to meet the standards of MIL-PRF-24385F, thus allowing the United States military to switch to a more environmentally friendly firefighting agent. By conducting this work, the project team has been able to comprehensively test and evaluate thirteen of the COTS PFF against both MIL-PRF-24385F and each other, and determine which best fit the needs of the Department of Defense (DoD).

The benefits to DoD from validating and demonstrating viable AFFF alternatives that are PFAS-free are (a) significant DoD operational and maintenance cost savings; and (b) a reduction in environmental risk. A preliminary economic analysis indicates that PFF cost about the same as AFFF concentrates, but the better performing PFF require about two times as much foam to extinguish gasoline fires, employing aspirating nozzles. However, CAF typically reduces the amount of PFF required by over 30%. So, the real benefit of employing a technology like CAF is in reducing the annual PFF purchase cost and wastewater treatment and disposal costs. It is estimated that the DoD-wide demand for PFF concentrates for FY25 is $1.12 million gallons per year, suggesting a potential DoD operational cost savings of as high as $70M/yr for foam purchase and wastewater treatment and disposal via CAF implementation. 

The estimated capital cost to implement CAF is $100M to $200M, which makes the potential investment worthwhile. The estimated Technology Readiness Level after completion of this project is 8/9, which should allow immediate implementation of the successful PFF DoD wide, thus helping to meet the National Defense Authorization Act passed by Congress in 2020 requiring that the military assess and then implement foam alternatives that do not contain perfluorooctanoic acid and perfluorooctanesulfonic acid. Additionally, this technology demonstration/validation will greatly help civil aviation reduce the environmental impact via use of fluorine-free PFF that meet or exceed the performance of currently used fire suppressants.

The initial step in stakeholder acceptance of this technology is the inevitable release of the new Mil-Spec in October 2023. If it is determined that CAF or UHP, or a combination of both, is required for PFF to achieve acceptable fire performance, modifications to existing systems will be required. Even if the new Mil-Spec can be met using conventional foam delivery, firefighters may choose to deploy CAF and UHP to reduce the quantity of foam required to extinguish fires. The United States Air Force Aircraft Rescue and Fire Fighting fleet is already equipped with UHP vehicles but is not so widely equipped with CAF. The CAF and UHP technologies are tools that may be more effective in some scenarios and less in others. It may not be necessary (or indeed practical) to retrofit every firetruck with both delivery systems so long as both capabilities are distributed across the response fleet. In future procurements as the firefighting fleet is updated, it is expected that such technologies will become integrated as standard requirements, but lifecycle and sustainment analysis would have to be extensively completed ahead of an acquisition plan.

For trucks currently in the fleet, existing hardware could have trouble proportioning PFF, as some of the new formulations are highly viscous. Regardless, every truck in the fleet that has operated with AFFF will need to be cleaned to remove the remaining fluorine. Furthermore, the firefighting techniques required to extinguish fires with PFF are somewhat different than the techniques used with AFFF, so firefighters may have to be retrained.

Chauhan, S., “Progress in Enhancing Mil-Spec Performance of mature PFAS-Free Foams,” presented in Foams and Emulsions; PFAS-Free Foams and Understanding Bubbles, SERDP-ESTCP Symposium, Enhancing DoD’s Mission Effectiveness, December 1, 2020.

Chauhan, S. and A. McMeans, “Performance of Next Generation of Firefighting Agents against Military Specification Criteria,” presented at AFCEC/CXAE 2^nd Annual Fire Protection Workshop, November 17, 2021.

Chauhan, S., “Demonstration of Selected Approaches for Enhancing Performance of PFAS-Free Foams,” presented at SERDP-ESTCP Symposium, Enhancing DoD’s Mission Effectiveness, December 1, 2021.

Chauhan, S., “Demonstration of Compressed Air Foam and Ultra High Pressure Firefighting with PFAS-Free Foams,” presented at SERDP-ESTCP Symposium, Enhancing DoD Mission Capabilities, November 30, 2022.