Carbon Monoxide Alarm Placement Guide: Where to Fit CO Detectors and What UK Regulations Require

Carbon monoxide alarms are one of the most important safety devices in any property with a fuel-burning appliance — and one of the most misunderstood. Gas engineers, electricians, and property managers regularly get asked where to fit a carbon monoxide alarm, which model to use, and what UK regulations actually require. This guide cuts through the noise and gives you the practical answers.

What Is Carbon Monoxide and Why Does It Kill?

Carbon monoxide (CO) is a colourless, odourless gas produced when fossil fuels — gas, oil, coal, or wood — burn incompletely. You cannot see it, smell it, or taste it. That is what makes it dangerous. In the UK, CO poisoning sends hundreds of people to A&E every year and kills around 50.

Common sources in UK homes and commercial properties include:

• Gas boilers (especially older or poorly serviced units)
• Solid fuel stoves and open fires
• Oil boilers and range cookers
• Gas water heaters
• Blocked flues and chimneys

Symptoms of CO poisoning — headaches, nausea, dizziness, confusion — are easily confused with flu or food poisoning. The key giveaway: symptoms improve immediately when you leave the building. If your customer reports that, treat it as a CO emergency.

UK Regulations: When Is a Carbon Monoxide Alarm Required?

This is where tradespeople often get caught out. Requirements differ by appliance type, property type, and which nation of the UK the job is in.

England and Wales — Building Regulations Part J

Part J requires a BS EN 50291-compliant CO alarm to be fitted whenever a new or replacement solid fuel appliance is installed. The 2022 update to the Smoke and Carbon Monoxide Alarm (Amendment) Regulations extended the requirement to all rented properties: landlords must fit a CO alarm in any room with a fixed combustion appliance — including gas boilers and oil boilers — with the exception of gas cookers.

Scotland — Technical Handbook (Domestic)

Scottish regulations are broader. CO alarms are required when installing any fuel-burning appliance, including gas and oil. The alarm must be placed in the room containing the appliance, in an enclosed boiler enclosure, or in any room where a flue passes through.

Northern Ireland — Technical Booklet L

Similar to Scotland: covers all fuel appliances except cookers, with the same placement requirements around appliance rooms and flue routes.

For Landlords in England and Wales

Since 1 October 2022, the amended regulations require a working CO alarm in every room used as living accommodation that contains a fixed combustion appliance (gas cookers excluded). Landlords are legally responsible for fitting and testing alarms at the start of each new tenancy. Non-compliance can mean a civil penalty of up to £5,000.

Where to Fit a Carbon Monoxide Alarm: Placement Rules

Get the position wrong and the alarm may not respond in time. Here is what the standards and manufacturer guidance actually say.

Mounting Height

CO is slightly lighter than air but disperses evenly throughout a room, so it can be fitted at head height (1–1.5m from the floor) or on the ceiling. If ceiling-mounted, keep it at least 30cm from any wall. If wall-mounted, keep it at least 15cm down from the ceiling. Unlike smoke alarms, CO alarms do not need to be on the ceiling — either position works.

Rooms to Cover

• Always fit in the room containing the appliance (boiler, stove, open fire, water heater)
• Bedrooms where the flue serving the appliance passes through, or where occupants sleep close to the appliance
• Hallways and landings to catch CO spreading from a boiler cupboard
• Living rooms with open fires or log burners need their own dedicated alarm

Where NOT to Fit

• Directly next to a gas cooker hob — excluded from the requirement, and cooking fumes can cause nuisance alarms
• In direct sunlight or against a heat source such as a radiator
• In bathrooms or shower rooms — humidity triggers false alarms
• Immediately next to doors, windows, or extractor vents — CO needs time to reach the sensor, not be diluted away

Battery vs Mains: Which Type of CO Alarm Do You Need?

Both battery-powered and mains-powered alarms are acceptable under UK regulations, provided they meet BS EN 50291-1:2018. The choice depends on the installation context.

Battery-powered units are the most common choice for retrofits and rental properties. Modern 10-year sealed battery models eliminate the problem of tenants removing or running down batteries. Fit anywhere with a single screw, no wiring required.

Mains-powered with battery backup suits new-build or renovation projects where the alarm can be wired in permanently. Harder to tamper with — preferred in HMOs and larger residential schemes where long-term compliance matters.

Interlinked wireless alarms make sense for larger properties where a CO event in a basement boiler room needs to trigger alarms on every floor. Several brands offer RF interlink that works alongside interlinked smoke alarms on the same network.

Trade Picks: CO Alarms We Stock at APM

We keep all the major brands in stock at our trade counter in Acton, W3. Here are the models our gas engineers and electricians reach for most often.

FireAngel FS1326-T — 10-Year Sealed Battery CO Alarm

The FS1326-T is one of the most widely fitted battery CO alarms in the UK trade. It runs on a tamper-proof 10-year lithium battery — no battery changes, no tenant interference. Smart RF-ready so it can be linked into FireAngel's wireless interlink system without rewiring. Meets BS EN 50291-1:2018. Wall or ceiling mount. Go-to for Part J compliance on new solid fuel installs and landlord retrofit jobs.

Kidde 2030-DCR — 10-Year Sensor Battery CO Alarm

Kidde's 2030-DCR is a compact, reliable standalone unit with a 10-year sensor life powered by 2 AA batteries. Green/amber/red LED status indicators let tenants self-check easily. 85dB alarm, test and hush button, wall or freestanding use. Well priced for multi-unit landlord orders. BS EN 50291 certified.

Honeywell Home R200C-1 — Standalone CO Alarm

The Honeywell R200C-1 is a professional-grade standalone alarm often specified on commercial and housing association contracts. Digital display shows current CO concentration in ppm — useful for diagnostics on site. Battery-powered with a peak level memory function so you can check what level was reached after an event. The right choice for any Gas Safe engineer who wants to hand the customer full visibility of what happened.

Browse the full range: Carbon Monoxide Alarms at APM — or see everything in our Safety & Alarms collection.

Pick Up Today from Acton, W3

All the alarms above are available for same-day collection at our trade counter at 24 Western Avenue, Acton, London W3 7TZ. Call ahead on 020 8702 8080 to check stock or place an order for delivery. We serve gas engineers, electricians, and property managers across West London — trade accounts welcome.