Quick answer
Smoke alarms: at least one on each storey of the property where there's a room used wholly or partly as living accommodation. Not one per room. One per storey, minimum.
CO alarms: one in any room used wholly or partly as living accommodation that contains a fixed combustion appliance, other than a gas cooker. Gas cookers are specifically excluded.
On day one of a new tenancy you must check every alarm is in proper working order.
Maximum penalty: £5,000. That figure is unchanged as at August 2026, despite several other landlord penalties rising this year.
Three bedrooms, a kitchen, a lounge and a gas boiler in a cupboard. How many alarms?
The answer is smaller than most landlords expect, and the CO rule in particular catches people out in both directions. Some over-fit and waste money. Some miss the one room that actually needs it.
The smoke alarm rule, in one line
Regulation 4 of the Smoke and Carbon Monoxide Alarm (England) Regulations 2015 requires that "a smoke alarm is equipped on each storey of the premises on which there is a room used wholly or partly as living accommodation."
Two things follow from that wording.
- It's per storey, not per room. A three-bed house over two floors needs a minimum of two smoke alarms, not five.
- A storey with no living accommodation doesn't count. An unconverted loft or a cellar used only for storage isn't caught. A converted loft bedroom is.
Note that bathrooms and toilets count as living accommodation for the purpose of deciding whether a storey is in scope, even though you wouldn't site an alarm in them.
The CO alarm rule, and the gas cooker exception
A CO alarm is required in "any room which is used wholly or partly as living accommodation and contains a fixed combustion appliance other than a gas cooker."
So the test has three parts. Is it a room used as living accommodation? Does it contain a fixed combustion appliance? Is that appliance something other than a gas cooker?
| Appliance | CO alarm required in that room? | Why |
|---|---|---|
| Gas boiler | Yes | Fixed combustion appliance |
| Gas fire | Yes | Fixed combustion appliance |
| Wood burner or open fire | Yes | Fixed combustion appliance |
| Oil-fired boiler | Yes | Fixed combustion appliance |
| Solid fuel stove | Yes | Fixed combustion appliance |
| Gas cooker or hob | No | Expressly excluded by regulation 4 |
| Electric heating throughout | No | No combustion |
| Portable gas heater | No (not required by these regs) | Not a fixed appliance. Fit one anyway. See the note below |
The gas cooker exclusion is real, and it surprises people. It reflects the fact that cookers are used intermittently and in ventilated spaces. That said, nothing stops you fitting one, and plenty of landlords do.
The 2022 change most guides still miss Before 1 October 2022, CO alarms were only required where there was a solid fuel burning appliance. Many older articles still say this. SI 2022/707 widened it to any fixed combustion appliance except a gas cooker, which brought gas boilers and gas fires into scope for the first time. It also extended the regulations to social housing and added a duty to repair or replace a faulty alarm as soon as reasonably practicable once a tenant reports it.
Worked examples
| Property | Smoke alarms | CO alarms | Total |
|---|---|---|---|
| Studio flat, one storey, electric heating, gas hob | 1 | 0 (gas hob is excluded) | 1 |
| One-bed flat, one storey, gas combi boiler in the kitchen | 1 | 1 (in the kitchen) | 2 |
| Two-bed flat, one storey, boiler in a hallway cupboard | 1 | See note below | 1 or 2 |
| Three-bed house, two storeys, gas boiler in the kitchen | 2 (one per storey) | 1 (in the kitchen) | 3 |
| Four-bed house, three storeys incl. converted loft, boiler in utility, wood burner in lounge | 3 (one per storey) | 2 (utility and lounge) | 5 |
| Five-bed HMO, two storeys | Minimum 2 by these regs, but licence conditions and the fire risk assessment will require considerably more | Per appliance | Per FRA |
The hallway cupboard question. The regulations tie the CO alarm to a room used wholly or partly as living accommodation. A cupboard isn't. But the safest reading, and the one most fire officers prefer, is to fit an alarm where the appliance is or in the adjacent space. It costs about £20 and removes the argument entirely.
Where to actually site them
The regulations say where alarms are required, not exactly where to mount them. For that, follow the manufacturer's instructions and BS 5839-6.
- Smoke alarms: ceiling-mounted, as central to the room or hallway as possible, at least 300mm from walls and light fittings. Landings and hallways are the standard positions since they're on the escape route.
- Avoid: kitchens and bathrooms for smoke alarms, because of false alarms from cooking and steam. A heat alarm is the right device for a kitchen.
- CO alarms: roughly 1 to 3 metres horizontally from the appliance, at head height or on the ceiling. Not directly above the appliance, not in a cupboard with it, not next to a window or door.
- Don't put a CO alarm in an unheated space like a garage. Temperature swings affect the sensor.
Hardwired or battery?
For the 2015 Regulations in the private rented sector, either is acceptable. The regulations don't specify the type or power source. What they require is that the alarm is present and in proper working order.
Two caveats worth knowing.
- Building regulations may require hardwired alarms in new builds, extensions and certain conversions. That's a separate regime from the landlord duty.
- HMO licence conditions frequently require a graded, interlinked system (often Grade D or a full Grade A fire alarm), which goes well beyond the 2015 Regulations. Your fire risk assessment drives this, not the alarm regulations.
Practically, sealed 10-year lithium battery alarms remove the single biggest failure point, which is a tenant taking the battery out.
Your duties on day one and during the tenancy
- Before the tenancy starts: make sure the required alarms are installed.
- On the first day of a new tenancy: check every alarm is in proper working order. Do this with the tenant present if you can, and record it in the inventory with a photo and the date.
- During the tenancy: the tenant is generally expected to test alarms regularly and replace batteries in non-sealed units.
- When a tenant reports a fault: if the alarm is found not to be in proper working order, you must repair or replace it as soon as reasonably practicable. That duty came in on 1 October 2022.
- Keep the evidence. A dated, signed inventory entry is what defends you if a penalty notice arrives.
What happens if you get it wrong
The council can serve a remedial notice, and if you don't comply, impose a penalty charge.
| Detail | |
|---|---|
| Maximum penalty charge | £5,000 (regulation 8(2)). Unchanged as at August 2026 |
| Time limit to serve | Within 6 weeks beginning with the day the authority is first satisfied of the breach (regulation 8(3)) |
| Right to review | You can request a review by the authority, and then appeal to the First-tier Tribunal |
| Council may act itself | The authority can arrange for the alarms to be fitted where you don't comply |
Worth flagging: several landlord penalties rose to £40,000 during 2025 and 2026. The smoke and CO alarm penalty did not. It's still £5,000. If you see £40,000 quoted for alarms, that's a bulk-update error in someone's content.
Licensed HMOs are different
The 2015 Regulations largely leave licensed HMOs to be dealt with under Housing Act 2004 licence conditions instead. In practice that means more, not fewer, obligations.
For an HMO your alarm requirements come from the fire risk assessment and the borough's licence conditions, which commonly specify a graded system, interlinked detection, emergency lighting on escape routes and annual certification.
See our guide on fire risk assessments for HMO landlords for what that involves.
Sources
- Smoke and Carbon Monoxide Alarm (England) Regulations 2015, reg 4 (where alarms are required, day-one check, repair duty)
- Regulation 8 (£5,000 maximum penalty charge, 6-week service window)
- SI 2022/707 (the 1 October 2022 amendment extending CO alarms to all fixed combustion appliances except gas cookers)
- gov.uk: Smoke and carbon monoxide alarms, explanatory booklet for landlords
- BS 5839-6 (fire detection and alarm systems in domestic premises) for siting and grading
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About the author
My Landlord Certificate Compliance Team
This guide was written and fact-checked by the My Landlord Certificate compliance team and reviewed against current UK legislation by our NICEIC-approved, NAPIT-registered, Gas Safe registered, accredited DEA and NEBOSH-qualified engineers. We help landlords across all 33 London boroughs stay compliant with fixed-price EICR, Gas Safety (CP12), EPC, Fire Risk Assessment and PAT testing.