The goal of this Limited Scope research effort is to develop new foam evaluation tools that will enable a more comprehensive understanding of per- and polyfluoroalkyl substances (PFAS)-free foam performance under extreme conditions. With the appreciation that fuel vapor composition is dynamic, existing laboratory-based techniques used to evaluate foam performance do not provide for the systematic understanding of foam failure as a function of vapor composition. As vapor composition is dynamic, and most effected by extreme conditions, it is critical to develop the proper tools to access foam performance. This work will demonstrate how the vapor composition of a fuel of interest varies as a function of temperature, determining the role that fuel composition has on the associated vapor. With that understanding, the project team will evaluate PFAS-free foam performance as a function of vapor composition, identifying the critical components of fuel vapor that compromise PFAS-free foam performance. By relating vapor composition to novel foam stability metrics, the goal is to realize a tool wherein standard fuel property surveillance will include the ability to determine the most suitable PFAS-free foam formulation for firefighting. This work will provide critical information in support of identifying the most suitable PFAS-free firefighting formulations for a given fuel and firefighting conditions.

The project's efforts will focus on defining vapor composition as a function of temperature and evaluating foam performance as a function of vapor composition. This work has three primary tasks: the determination of the composition of fuel vapor headspace as a function of temperature, the development of a fuel vapor testbed for the quantitative generation of fuel-based vapor streams, and the use of those streams in the generation of PFAS-free foams for laboratory-based evaluation. Briefly, using a combination of Solid Phase Micro Extraction, direct vapor sampling, and gas chromatography-mass spectrometry, the project team will identify the primary components of fuel head space as a function of temperature. This will inform the development of a vapor generation testbed that provides quantitative vapor streams of single components and/or mixtures of fuel related vapor. These vapors will be used to generate foams that will, in turn, be evaluated using traditional laboratory techniques (e.g. Dynamic Foam Analysis). By generating the foams from the fuel vapor stream, the project team anticipates reducing the time necessary to determine the suitability of a foam for fighting specific fuel fires.

The co-development of a fuel vapor testbed and new approach to evaluating PFAS-free foams will reduce the time necessary to comprehensively understand the role of fuel vapor composition on foam performance. Those components most disruptive to the foam can be identified and screened across different firefighting foam products to determine which foams are less sensitive to specific components. Long term goals, beyond the scope of this project, include the ability to analyze fuel composition to establish the most suitable PFAS-free foam formulation as a function of fire conditions.