Fire and CO alarms: the rules aren't the same in England, Wales and Scotland

You are pricing a job that needs smoke alarms fitting, or a customer asks if their alarms are "up to standard." Simple enough, until you realise there is no single UK rule. Fire and carbon monoxide alarm requirements are set separately in England, Wales and Scotland, and they are not the same. Where the alarms go, whether they have to be interlinked, and which appliances need a CO alarm all change depending on which side of a border the job is on.

Get it wrong and the work is not compliant, even if you fitted a perfectly good alarm. So here is what the law actually asks for, in plain English.

The short version

• There is no single UK rule. England, Wales and Scotland each set their own fire and CO alarm requirements.
• Scotland is the strictest and it applies to every home, owned or rented: interlinked smoke alarms plus a heat alarm in the kitchen.
• Wales requires mains-wired, interlinked smoke alarms on every storey in rented homes.
• England rented homes need at least one smoke alarm per storey, and they do not have to be interlinked or mains-wired.
• A CO alarm goes wherever there is a fuel-burning appliance, but the exact rule on which appliances differs by nation.

Here is what sits behind that, and where trades get caught out.

The three jobs: smoke, heat and CO

Three different alarms, three different jobs, and people mix them up.

A smoke alarm detects smoke from a fire. A heat alarm detects a rapid rise in temperature and is used in kitchens, where a smoke alarm would go off every time you cook. A carbon monoxide alarm detects the invisible gas given off by fuel-burning appliances like boilers, gas fires and wood burners. A CO alarm is not a smoke alarm and does not replace one.

Smoke and heat alarms for homes are made to British Standard BS 5839-6. CO alarms are made to BS EN 50291. If an alarm does not meet the right standard, it does not count, whatever it cost.

There is no single UK rule

This is the part that catches people out. Fire safety in homes is devolved, so each nation writes its own rules. An install that is fine in England can fall short in Scotland or Wales, because the bar is set in a different place.

If you work near a border this matters even more: the same customer expectation, the same type of alarm, and two different legal requirements depending on which side you are on. We cover that border problem in more depth for England and Scotland.

The rules, nation by nation

Scotland: every home, interlinked

Scotland has the broadest rule, and it is the one most people underestimate. Since February 2022 every home in Scotland, owned or rented, must have:

• one smoke alarm in the main living area, usually the living room,
• one smoke alarm in every hallway and landing,
• a heat alarm in the kitchen,
• all of those interlinked, so when one sounds they all sound.

If there is a carbon-fuelled appliance such as a boiler, fire or wood burner, that room also needs a CO alarm. The CO alarm does not have to be interlinked. You can meet the rule with sealed long-life battery alarms, which can be fitted without an electrician, or mains-wired alarms, which must be fitted by a qualified electrician.

Wales: mains-wired and interlinked (rented homes)

In Wales, rented homes covered by the Renting Homes rules need a working smoke alarm on every storey, mains-wired and interlinked. Since December 2022 a CO alarm is also required in any room with a gas, oil or solid-fuel appliance, and in Wales that includes a gas cooker.

England: one per storey (rented homes)

England is the lightest touch of the three. In rented homes the rule is at least one smoke alarm on every storey that has a room used as living accommodation. A CO alarm is required in any such room with a fixed combustion appliance, but gas cookers are excluded.

The gap to watch: in England rented homes the alarms do not have to be interlinked or mains-wired. That is the legal minimum, not best practice. A single alarm per floor can still leave someone asleep upstairs who cannot hear an alarm sounding in the kitchen. Plenty of landlords ask for the minimum. It is worth telling them what the minimum does and does not do.

New builds and big renovations follow building regs, not these rules

One more trap. The rules above are mostly about existing homes, rented or, in Scotland, owned. The moment you are on a new build, an extension or a material alteration, building regulations take over, and they carry their own alarm requirements, which differ by nation too. If the job needs building regs sign-off, check what the alarm spec has to be for that work, not just the housing rules. The same goes for gas appliances and CO.

The full room-by-room breakdown for all three nations, owned and rented, is in our guide: Fire and CO alarms in England, Wales and Scotland.

Common questions

Does every home in Scotland really need interlinked alarms, even if the owner lives there?

Yes. Scotland's rule applies to all homes, not just rentals. It is the main thing that surprises people, because England and Wales tie most of their requirements to rented properties.

Can I fit the alarms myself or does it need an electrician?

Sealed long-life battery alarms can be fitted without an electrician. Mains-wired alarms must be installed by a qualified electrician, and in England electrical work like that can fall under Part P. If in doubt, use a registered electrician.

Is a smoke alarm enough, or do I need a CO alarm as well?

They are separate jobs. A smoke alarm does not detect carbon monoxide. If there is a fuel-burning appliance in the room, you need a CO alarm too. Which appliances trigger the requirement differs by nation.

What standard should the alarms meet?

Smoke and heat alarms for homes should meet BS 5839-6. CO alarms should meet BS EN 50291. An alarm that does not meet the standard does not count towards the legal requirement.

The bottom line

There is no UK-wide fire alarm rule, and treating England, Wales and Scotland as the same is how compliant-looking work ends up non-compliant. Know which nation's rules apply, fit to that, and when a customer wants the bare minimum, tell them plainly what it does and does not protect. For the full room-by-room requirements in each nation, owned and rented, use our guide: Fire and CO alarms in England, Wales and Scotland.