The acronym PFAS is short for per or polyfluoroalkyl substance. Depending on the source, there are up to 15,000 products or materials that meet the definition of PFAS. PFAS includes a broad category of materials that can be solids, liquids or gasses. Some fire protection materials, defined as PFAS, that are components in aqueous film forming foams (AFFF) are considered persistent, bioaccumulative, and toxic (PBT). Because of this, their use in fire protection and other applications is being phased out globally by the U.S. EPA and other regulatory agencies.