Fire doors mayt be vulnerable to the intense heat transferred through the mass of metal that door hinges and latch plates represent. This can cause charring and ignition. Intumescent plugs, comprising a short length of metal tubing filled with intumescent material, are used to protect these ares by preventing the passage of flaming or hot gases by smothering the surrounding areas on activation.

The plugs are located in holes drilled through hinges, striker plates and pivot mechanisms (as shown above).