Fire doors are an essential component of a building's fire safety measures. Whilst gaps round the edge of doors are needed to allow the doors to open, they are the fire resisting doorset's weakest point. These Intumescent Fire Door Seals, or Intumescent Strips, are designed to protect the edges of fire doors when fire strikes. When exposed to hot smoke or flames, the seals swell up and firmly seal the gap, preventing the passage of fire, hot gases and smoke. The brush 'cold smoke' seal also protects against smoke spreading through a building, which has a massive detrimental effect on safe and rapid evacuation in an emergency.