Fire protection for cable ducts - by void filling foaming material in plastic foils between asbestos foam plates

Ducts in which cables are passed through walls of buildings are given fire protection by designing the ducts as sheet metal channels to which a flat lid is fixed by bolts. The ends of the duct are sealed by plates of asbestos foam material. The voids left by the cables are filled by strips of aqueous sodium sili-cate, reinforced by glass fibre or tissue, coated on both sides with epoxy resin and enclosed in a waterproof CO2-tight foil. The material preferred for this foil is PA/PE with a thickness of 90-150 mu. The foam plates are sealed by silicone rubber. This system is easy to apply and provides reliable protection.