Everbuild EVBEVFIRE firefoam B1 is a quick setting one-part polyurethane foam with fire retardant properties. The foam expands on application to up to 50 times its original volume & meets the extremely stringent requirements of DIN 4102 Part 1 for Construction Materials; Class B & BS476 Part 20 (1987) where fire ratings of 30 mins to 3.5 hours are achievable.