AIS FR Graphite Sealant FP 501 is a high specification formulation designed to prevent the spread of fire, smoke and gases through openings in fire rated walls and floors. FP501 expands when it is subjected to fire and closes openings around penetrations when any combustible or low temperature melting materials have burnt away.

FP 501 is designed to fire seal difficult services which traditional fire rated mastics do not achieve such as large plastic pipes.

FP 501 can be used with a suitable filling material, i.e. stone wool or AIS backing material in order to ensure correct width to depth ratio and to reduce the shrinking of the sealant during curing. Minimum depth and maximum width of the joints are included in the installation instructions. Thermal activation takes place at 150 °C when the material will expand (intumesce) to prevent the passage of fire and smoke for periods up to 4 hours.

The sealant has undergone tests to BS EN 1366-3 for fire protection joints and the durability class is Z₂ intended for use at internal conditions with humidity classes other than Z₁.