In reality, people are more often affected by smoke before the fire itself. Fire doors are a lifesaver in this scenario because they can withstand smoke and fire. The smoke seals, for example, around the door edge and frame seal the gaps to prevent the smoke getting through, preventing smoke inhalation. Similarly, intumescent strips expand to several times their original size when exposed to heat to seal the gaps around the door to contain the fire and smoke.

They are an extremely important part of your buildings fire safety strategy.