Smoke and CO alarm rules for rented property
Alarm compliance is the cheapest legal duty a landlord has — £50 of hardware on a standard let — and one of the most enforced, because a missing alarm is visible to any council officer in thirty seconds. Here's exactly what England requires, who's responsible for testing once the tenancy starts, and where HMOs differ.
By the FixQuotes editorial team
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Key takeaways
- England requires a smoke alarm on every storey with living accommodation, and a carbon monoxide alarm in any room with a fixed combustion appliance, excluding gas cookers.
- Every alarm must be checked working on the day a new tenancy begins. During the tenancy, tenants test and change batteries; once a fault is reported, the landlord must repair or replace it as soon as reasonably practicable.
- Councils enforce with remedial notices and fines of up to £5,000 per breach.
- Battery alarms are legal in England. Government guidance recommends sealed-for-life batteries, and points to BS 5839-6 for smoke alarms and BS 50291 for CO alarms.
- Licensed HMOs are dealt with through licence conditions instead, and councils typically require interlinked mains-powered Grade D systems. Scotland and Wales have stricter rules.
What alarms does a rented property legally need?
Two duties cover almost every rental in England, under the Smoke and Carbon Monoxide Alarm (England) Regulations 2015 as amended in 2022. First: at least one smoke alarm on each storey where there's a room used wholly or partly as living accommodation — and for the storey test, bathrooms count as living accommodation, so a storey with only a bathroom still needs an alarm. Second: a carbon monoxide alarm in any room used as living accommodation containing a fixed combustion appliance — boilers, gas fires, log burners, oil stoves — with gas cookers the one exception. The exact wording is in regulation 4 of the 2015 Regulations.
Note what triggers the CO duty: the appliance, not the fuel supply. A flat with a combi boiler in the kitchen needs a CO alarm in the kitchen. A property with no fixed combustion appliance at all — all-electric heating, no fireplace — needs no CO alarm, however many gas neighbours it has.
These rules sit alongside, not instead of, your other safety duties — the annual gas safety check still covers the appliances themselves.
Who is responsible for testing the alarms?
The split is clean and worth putting in your tenancy welcome notes. On day one of a new tenancy: the landlord (or agent) must check every required alarm is in proper working order — press the button, record it, ideally on the inventory with a photo. During the tenancy: the government's explanatory booklet advises tenants to test alarms regularly and replace batteries themselves.
Once a tenant reports a faulty alarm (and new batteries haven't fixed it), the duty flips back: the landlord must repair or replace it as soon as reasonably practicable. Keep the report and your response in writing — the dated email trail is your evidence of compliance.
Enforcement runs through the council: a remedial notice first, then a penalty of up to £5,000 per breach if you don't comply, and the council can arrange the work itself. Per breach means a property with a missing smoke alarm and a missing CO alarm is two breaches, not one.
Do alarms need to be mains-wired? Which standards apply?
In England, no — the regulations don't specify the alarm type, so battery alarms are legal. Government guidance recommends sealed-for-life battery alarms over replaceable-battery models (nobody can quietly harvest the battery for the TV remote), and points to BS 5839-6 compliance for smoke alarms and BS 50291 for CO alarms.
Cost-wise this is the cheapest compliance on your list: sealed battery smoke alarms run £5 to £15 each and combined or CO units £20 to £50, so a typical two-storey house with a boiler is compliant for £20 to £80 in hardware, DIY-fitted. Mains-wired installation by an electrician runs roughly £100 to £200 per alarm — worth doing at rewire or refurbishment time, and the better baseline for portfolios.
Scotland and Wales are stricter, if you let across borders: Scotland requires interlinked alarms in every home (smoke in the most-used room and every hallway, heat in the kitchen), and Wales requires mains-wired, interlinked smoke alarms in rented homes.
What's different for HMOs?
Licensed HMOs are handled through their licence conditions rather than Parts 1 to 5 of the 2015 Regulations — but the practical bar is higher, not lower. Councils typically require an interlinked, mains-powered Grade D system to BS 5839-6 — every alarm with battery back-up, all sounding together — with heat alarms in kitchens, and Grade A panel systems in larger or higher-risk HMOs. The exact specification is in your licence and your council's HMO standards, and it ties into the wider fire-safety package of fire doors and protected escape routes.
Unlicensed HMOs — smaller shared houses below the licensing thresholds — stay under the standard 2015 Regulations, though the council can still require more through HHSRS if the risk justifies it. Our HMO compliance checklist puts alarms in context with the rest of the list.
If alarm installation is the job — a Grade D interlinked fit-out, or adding CO alarms across a portfolio — FixQuotes returns three quotes for the same job from qualified local electricians, free for landlords and letting agents. Start at our electrical quotes page.
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