In a flat, the floor and the walls between homes are there to hold fire back. Copper pipes and a drain through that floor are a hole in that defence unless the hole is fire-stopped for those pipes and that construction. A can of general gap filler is not a specification. England's usual guidance is Approved Document B. Scotland and Wales use their own fire rules.
The hole matters more than the copper
A split needs pipes between the indoor unit and the outdoor unit, and a drain for condensate. In a house those holes are mostly a making-good job. In a flat they often pass through a compartment floor or a compartment wall, the parts of the block that are supposed to resist fire for a stated period. Leaving them stuffed with ordinary foam, or open around the insulation, is how a small penetration becomes a path for smoke. The air conditioning is incidental. The compartmentation is the point.
Ask for a stated method, not a squirt
Fire-stopping is chosen for the pipe material, the diameter, the insulation and the wall or floor it passes through. The person doing it should be able to name the system they are using and where it is allowed to be used. This page will not name a product or a collar size, because copying a detail from a different wall is how stopping fails. If your installer subcontracts that seal, the quote should say so. If they say they will foam it on the way out, ask what fire performance that foam is claiming for this hole. A blank look is a reason to pause.
The managing agent will ask to see it
Leases commonly require consent for work that cuts structure or affects shared parts. The Leasehold Advisory Service explains leaseholder and freeholder consent in general terms. A managing agent on a cladded or recently remediated block may also want the penetration detail before anyone drills. That is not the same as planning permission for the outdoor unit. You can need both, or the lease and not the planning, depending on the building. Get the agent's question answered before the day the core drill is booked.
Use the fire book for the nation the flat is in
Approved Document B is guidance for England. A flat in Scotland or Wales is not excused from fire-stopping, and it is not helped by quoting the English document as if it were UK-wide. Ask the designer or the building control body for that address which standard they want the seal to meet. F-gas certification covers the refrigerant work. It does not, by itself, prove the fire seal. They are different duties that happen to fall on the same morning if nobody has separated them.
Frequently asked questions
Can the installer foam the hole and move on?
Only if that product is actually specified for this pipe and this floor or wall, and someone will stand behind that choice. General gap foam is a common shortcut and a poor one in a compartment.
Does a house need the same fire-stopping as a flat?
A house can still have fire-resisting floors, for example with a flat over a garage or a specified floor over a habitable room. Do not assume a house has no rule, and do not paste a block-of-flats detail onto a terrace without looking.
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How this guide was prepared
This guide was written by the Local AC Installers Editorial Team. We compare official guidance, legislation and established consumer information, separate general information from project-specific advice, and show publication dates and sources. We do not accept installer accreditation claims at face value.