The Science In Fireproof Doors
 Fire safety doors (like all school classroom doors in your
school) are all fitted with an intumescent strip.
 In the case of a fire the intumescent strip will seal the door
into the doorframe, preventing the fire from spreading
 The flow of oxygen that feeds the fire is cut off by this process
 The intumescent strip is made from a material
that rabidly expands when it is exposed to a high
heat
 On the left is an intumescent strip before being
heated, on the right is after.
 The strip seals any cracks around the door, now
to open it you need to cut the door down