For most latched single-leaf, single swing 30 minute (FD30S) timber fire resisting door assemblies, a single 10 mm x 4 mm or 15 mm x 4 mm strip of Therm-A-Stop down each jamb and across the head will usually be satisfactory.
Most latched single-leaf, single swing 60 minute (FD60S) timber fire resisting door assemblies will satisfy the requirements of BS476 : parts 20 and 22 (1987) test procedures when fitted with a single 20 mm x 4 mm strip across the head and down both jambs.
Tests carried out to BS EN 1634-1 often require more specific solutions e.g. twin 15 mm x 4 mm seals to achieve a 60 minute rating.
The intumescent foam produced by Therm-A-Stop is designed to withstand high temperatures, so it is well suited to applications incorporating timber doors with steel frames where conventional intumescent foam compounds break down.