The short answer
A fire collar is a steel shell filled with intumescent material that clamps around a plastic pipe where it passes through a fire-resisting wall or floor. In a fire the plastic softens and the intumescent swells, crushing the pipe and closing the hole. Plastic pipes through compartment walls and floors usually need one, or another tested seal such as a wrap, and the collar must be tested for that pipe, that size and that wall or floor.
On this page
Plastic soil stacks, waste pipes and water pipes run through almost every floor of a block of flats. Where they cross a compartment wall or floor, each one is a hole that will open up in a fire as the plastic melts. A fire collar is the most common way to close it.
How a fire collar works
A typical collar is a steel shell, often galvanised, lined with a graphite-based intumescent material. It wraps round the pipe and is fixed to the wall or the underside of the floor.
When fire reaches it:
- The plastic pipe softens and starts to collapse.
- The intumescent material swells many times its size.
- The steel shell stops it expanding outwards, so it pushes inwards, crushing the soft pipe and filling the hole.
The result is a solid plug of char where the pipe used to be, which holds back fire and smoke for the collar’s rated time.
When a pipe needs a collar
As a rule of thumb, any plastic pipe that passes through a fire-resisting wall or floor needs a tested seal. A collar is one option; intumescent wraps and some sealants and batt systems are others.
Some people still believe pipes under 40 mm do not need sealing. That is a misreading. Approved Document B expects openings for services in compartment walls and floors to be sealed or fire stopped so that the fire resistance is kept; follow the tested system for every penetration, however small the pipe.
Metal pipes do not melt in the same way, so they are usually sealed with mortar, sealant, batt or a wrap that deals with heat conducted along the pipe, not a collar.
Choosing the right collar
A collar is only as good as the test it relies on. Check that it was tested with:
| Check | Why it matters |
|---|---|
| Pipe material | PVC, polypropylene and polyethylene behave differently in a fire |
| Pipe diameter and wall thickness | Collars come in sizes and must match the pipe’s outside diameter |
| Wall or floor type | Masonry, concrete, plasterboard and batt systems each need their own test |
| Rating | The collar must match the wall or floor, such as 60 or 120 minutes |
| Pipe end conditions | Whether the pipe was tested open or capped at each end |
Manufacturers’ published data sheets typically cover plastic pipes from about 32 mm to 160 mm outside diameter, with ratings of up to 120 minutes in walls and up to 240 minutes in floors depending on the arrangement, tested to BS EN 1366-3 and classified to BS EN 13501-2. Always check the data sheet for the specific product rather than assuming.
Fitting: the common mistakes
Most failures found on surveys are installation errors, not bad products.
- Wrong side. In floors, collars are normally fixed to the underside, where fire would attack. In walls, many systems need a collar on both sides. Follow the maker’s instructions.
- Wrong fixings. Collars need the fixings and anchors the test used, into a substrate that can hold them in a fire.
- Gap not filled. The annular gap between the pipe and the hole often needs filling with a sealant or mortar before the collar goes on.
- Too close together. Pipes and collars bunched together can stop each other working. Systems set minimum spacings.
- Wrong size. A collar for a 110 mm pipe on an 82 mm pipe will not close it.
- Disturbed later. Collars removed or knocked off by other trades and never replaced.
How to check what you have
A compartmentation survey records every penetration in risers and voids, whether it is sealed, and with what. A good survey photographs each collar and checks it matches a tested system. If you have a record from the original installer, it should show the product, the test evidence and a label for each penetration.
Who should fit them
Anyone can buy a collar, but the seal has to be fitted exactly to its test. Many clients ask for a fire stopping contractor with third-party certification under a recognised installer scheme, who will photograph and label each one. Check the certificate number on the scheme’s own register.
Questions people ask
Can I fit a fire collar myself?
In your own home you can, but follow the maker’s instructions exactly. In a block of flats or a commercial building, the work is part of the building’s fire safety, so use a competent installer and keep the record.
Do fire collars expire?
They do not have a fixed expiry, but they can be damaged, corroded or disturbed. Check them as part of regular compartmentation inspections.
Is fire foam an alternative to a collar?
Not for plastic pipes in most cases. Some foams are tested with small plastic pipes in particular walls, but most plastic pipe penetrations need a collar or wrap. Use what the test evidence supports.
This bulletin is general guidance, not a design or specification.