For fire and smoke-control door assemblies, intumescent material addresses two essential needs:

• Positive-Pressure Fire Door Testing

   Wherever positive-pressure conditions are required for fire-door tests, intumescent material provides a simple, economical solution for wood doors by effectively changing the condition of the test. As superheated gases from the test furnace are forced by positive pressure through gaps in the door openings, expanding intumescent material seals off the spaces and contains the circulation of hot gases. Because flames and hot gases are now contained in the furnace, the intumescent barrier protects the edges and unexposed surface of the door, which assists the door assembly in passing the test.

   Metal foam-core fire door assemblies are also subject to increased risk of test failure under positive-pressure conditions. Sizable gaps between door and stop can result from the tendency of metal to change shape at extreme temperatures, allowing flames to be visible on the unexposed side of the door. In addition, the highly flammable foam cores emit volumes of smoke and flames which must remain in the test furnace. These gaps can be effectively sealed by intumescent action.

• More Effective Smoke Control

   The additional demands for smoke-control performance due to adoption of revised NFPA 105 guidelines and test standards by UBC 7-2 ,1997 can be satisfied fully and at reasonable cost with intumescent material. At 400^oF (204^oC) "warm smoke" temperatures, intumescent seals compensate for lost sealing capability in conventional gaskets and any gaps caused by metal distortion, virtually eliminating smoke leakage.