The Department of Defense (DoD) has many fire suppression systems, including aircraft rescue and firefighting (ARFF) vehicles, possibly impacted by residual entrained per- and polyfluoroalkyl substances (PFAS) resulting from the use of aqueous film-forming foam (AFFF). PFAS are known to self-assemble and coat surfaces at liquid/solid interfaces to form waterproof coatings and can therefore be difficult to fully remove from surfaces. If integrated ARFF foam systems are not properly cleaned and replacement PFAS-free foam is added, PFAS may dissolve from the surfaces of the system and release into the new foam. Recent experience has demonstrated that low-pressure water-only rinses may not adequately clean some systems or system components. However, the cost of replacing all existing PFAS-impacted AFFF delivery infrastructure across DoD installations would be expensive and result in facility downtime. Development of effective and standardized data-driven methods to remove PFAS from existing infrastructure would serve to reduce cost and operational impact. Effectively removing PFAS from infrastructure without complete replacement will have widespread application for DoD. This project will systematically evaluate the cleaning of a fire suppression system on an ARFF vehicle provided.

For this project, the ARFF vehicle will be flushed with a series of water flushes with the existing system in place. The PFAS level in the rinsate will be measured after each flushing event to provide information on cleaning effectiveness and efficiency. Following water flushing, the onboard foam system will be dismantled and wetted parts will be replaced. Removed parts of the fire suppression system will be sent to a laboratory for testing to determine the residual PFAS concentrations on the wetted surfaces of the individual parts. Data will be analyzed to determine the effectiveness of water to remove PFAS from wetted surfaces. Data also will be used to determine the respective PFAS contribution of individual wetted components to the total PFAS mass in the system. Project data will be analyzed and used to support the assessment of the cost-benefit relationship between cleaning versus replacement and to develop protocols for foam replacement.

Disassembly of fire response vehicles for complete parts replacement is expected to be a cost-prohibitive process, requiring extensive equipment downtime and labor to complete. This project will result in the complete characterization of PFAS impacts within an ARFF vehicle. By understanding the locations of PFAS impacts in the ARFF vehicle and the magnitude of the PFAS in each component, a cost-controlling decision can be made to determine the extent of disassembly, if any, required to adequately remove PFAS as part of foam transition activities. (Anticipated Project Completion - 2024)