Tested following the principles of BS 476 part 20 (1987) as detailed in Warrington fire research report No. 144508/B (Feb 2005). The product, in suitably designed joints, will resist the passage of fire for up to 5-hours. The selected fillers used in this formulation also make it suitable for use as an acoustic sealant. When exposed to heat, it swells greater than 3 x its original size, so creating a char that will resist the passage of fire for up to 5 hours and no priming is required for most construction substrates. The Everbuild fire sealants are for use in joints up to 50mm wide and give excellent acoustic properties for sound deadening and the sealant is easy to apply and tool off for the perfect finish. Fast cure – tack free in 15-minutes, can be overpaintable.