Beyond doors and sealant, a family of intumescent products exists to deal with the specific holes buildings need: pipes through walls, cable trays through compartments, glass in a fire door, and a letter plate in a flat entrance door. Each is a tested product for a tested situation, and each fails the same way if it is used somewhere it was never tested.
Pipe collars
A plastic pipe passing through a fire compartment wall is a hole waiting to happen: the pipe softens and burns away, leaving an open route for fire. A collar fitted around the pipe at the wall contains intumescent material that expands inwards as the pipe softens, crushing the pipe closed and sealing the opening. Collars are sized to the pipe and tested for particular wall constructions and pipe materials.
Pillows and batt
Large service openings carrying cable trays and bundles cannot be sealed with mastic. Intumescent pillows are packed into the opening around the services and expand in heat to close the remaining voids, and are used where services change often because they can be removed and repacked. Coated batt systems do the same job permanently and are used where the arrangement is stable. Both are tested as systems, and mixing components between manufacturers voids that.
Glazing tape and beads
Glass in a fire door or screen is held by a system: the glass type, the bead, the fixings and an intumescent glazing tape or seal around the perimeter, all tested together. The tape expands to hold the glass in place as the frame moves in the fire. Reglazing a fire door with ordinary glazing materials is a very common and completely invisible way to destroy its rating.
Letter plates
A letter plate is an aperture through a flat entrance fire door, and an intumescent letter plate carries material that closes the opening in heat. Fitting an ordinary letter plate into a fire door leaves a hole at hand height in a door protecting the only escape route from a flat. This is a recognised defect in blocks of flats and it is one of the items a flat entrance door check should be looking for.
Questions people ask about intumescent collars
Do plastic pipes through a fire wall need a collar?
Generally yes. A plastic pipe softens and burns away in a fire, leaving an open hole. A collar sized for the pipe and tested for that wall construction closes the opening as the pipe fails.
Can I reglaze a fire door with ordinary glass?
No. The glass, beads, fixings and intumescent glazing tape are a tested system. Reglazing outside that system invalidates the door's rating and it is impossible to see afterwards.
Does a flat entrance fire door need a special letter plate?
If it has a letter plate at all, it needs an intumescent one tested for fire doors. An ordinary plate leaves an opening through a door protecting the flat's only escape route.