Specifically designed for sealing around service penetrations in walls and floors, a single Astroflame board (60mm thick) can provide high levels of fire integrity and insulation offering up to 4 hours resistance in accordance with BS4746: Part 20: 1987. Astroflame Boards consist of a mineral fibre core coated on both sides with Astroflame Mastic, which transforms into a hard ceramic during a fire to prevent the passage of fire and smoke and the transfer of heat.