Current state of knowledge regarding PFAS-contaminated fire-fighting equipment   Since the discovery of per- and polyfluoroalkyl substances (PFAS), these have been a common additive in fire-fighting foam concentrates. This is because PFAS add properties that improve extinguishing performance, particularly against pool fires. PFAS constitute a group of substances, several of which have been shown to have negative health effects; furthermore, PFAS do not break down in nature (or do so only very slowly or to a limited extent). In addition to the negative health effects, increasingly strict legal requirements are gradually forcing a transition to PFAS-free fire-fighting foam. Today, there are PFAS-free fire-fighting foams developed for pool fires with sufficiently good performance, and there is normally no reason not to switch to PFAS-free foams. Several studies have highlighted challenges with this transition – despite cleaning equipment, PFAS remain on the surfaces of fire-fighting equipment materials, and residual PFAS will slowly leach over time and contaminate the product that is intended to be PFAS-free (so-called PFAS rebound). This report provides a summary of the legal requirements as well as an overview of the tests that have been conducted to clean equipment and limit PFAS rebound. Factors that appear to improve the cleaning effect include elevated temperature, scrubbing/high-pressure washing, and the addition of solvents (e.g., methanol, ethanol, and butyl carbitol). pH is also noted to influence cleaning, and it may be necessary to combine washes with both high and low pH. Furthermore, the report concludes that cleaning is needed to meet the levels proposed in the requirements, and that complete cleaning is not considered possible based on current knowledge.