Fluorosurfactants have been used effectively in ﬁreﬁghting foams since the 1960’s. However, increased concern by regulators and the public over the impact of per- and polyﬂuoroalkyl substances (PFAS) is changing the way firefighting foams are managed and regulated. Newly developed foams known as C6 foams, are proposed as ‘environmentally improved’ replacements, yet these replacements still contain significant amounts of short-chain PFAS, six perfluorinated carbons and less, that are currently regulated in several countries. Foam users have been turning to ﬂuorine free foams (F3) to maintain effective fire protection while better managing environmental liabilities, reputational risk and possible 3rd party litigation. The increased extinguishment performance of the new generation F3 have made them viable alternatives to fluorosurfactants for many applications and are currently in use as training foams, aviation applications in hangars and helipads, and chemical and bulk fuel storage systems. Recent independent tests evaluating the performance of F3 by LASTFIRE to extinguish increasingly larger diameter ﬁres have been very successful in Europe (2017) and more recently at the Dallas Fort Worth Airport (2018). Successful foam transition takes a well-developed, site-speciﬁc strategy. Some of the considerations associated with foam transition include: Maintaining compliance with ﬁre protection regulations and insurance accreditation; Competent foam selection based on independent certifications, performance testing and analytical testing for composition; Maintaining a functional ﬁre suppression system to protect human health and assets; Understanding of the design basis and operational knowledge of existing equipment; Compatibility assessment of system components with new foam; Eﬀective decontamination of existing equipment to remove residual PFAS and prevent cross-contamination of new foam; Proper planning for containment and disposal of waste generated during transition; Eﬀective secondary containment, and inspection and maintenance procedures are required; and, Proportioning testing to establish performance of new foam. Observations, results, data, and lessons learned from foam transition projects will be presented for various fire protection applications ranging from aviation hangars, to bulk fuel storage and chemical manufacturing. From an environmental perspective, effective cleanout of residual PFAS from previous aqueous film forming foams (AFFF) usage is critical for a successful transition. Contamination of new foam from residual can render it no longer PFAS-free, creating future liabilities. While every system is different and requires assessment, water rinses alone have often been found to be ineffective. Biodegradable, nontoxic solvents have been developed and applied to piping and tank systems to achieve greater PFAS removal, which have greatly improved the mass removal of PFAS from a stainless-steel tank over that of water alone. Total oxidisable precursors (TOP) assay used to test flush water for PFAS content has highlighted the limitations of using only the standard PFAS analysis on foam-impacted fluids. Ian Ross, Senior Technical Director, Arcadis UK Ian Ross, PhD, is a senior technical director with Arcadis and the company’s global PFAS lead. He has focused on remediation for more than 25 years, designing and implementing innovative chemical, physical, and biological remediation technologies. He is currently focused on risk management and remediation of PFAS, with more than 14 years of experience working on PFAS projects.