Intumescent Materials
Intumescent means tumour forming. What on earth would you want one of those for in DIY?
Intumescent Materials are used for fire protection. On exposure to fire, the items swell up to form a fire and smoke resisting foam that will block fire spread for anything upto an hour.
Intumescent Products
Door seals
These are strips that go into grooves routed into the sides and top of a door. These are a common sight in large buildings.
They prevent fire spread from room to corridor, or vice versa, and protect occupants in other rooms from the smoke, which can be toxic.
Downlighter hoods
These hoods sit on downlighters fitted in ceilings. Downlighters penetrate the fire & smoke barrier, and the intumescent hood restores this layer of protection. In a fire the hood swells and blocks the hole.
Paint
Flammable surfaces in need of fire protection where no visible bulk would be acceptable can be painted with intumescent paint. It isn't cheap.
Varnish
Woodwork can be painted with clear intumescent varnish to create an invisible fire barrier.
Sealant
May be used to add fire resistance where materials are joined.
Putty
Non setting putty fills gaps where pipes pass through walls. It allows pipe movement, and can be removed and reused if ever necessary.
Oak
Oak is intumescent, in a fire it forms a layer of fire resistant char, delaying consumption. This feature is occasionally made use of in building design, and is the reason oak was used for electrical wiring accessory backing plates long ago.