Quick answer: Get the FireAngel FA3322 Digital CO Alarm (~£20–28). It has a sealed 10-year battery, passes EN 50291 certification, and requires no battery changes for its entire working life. If you rent, your landlord is legally required to fit one in any room with a fixed combustion appliance — if they haven't, tell them. If you own your home, fit one anyway. CO has no colour or smell; an alarm is the only reliable warning.
Is a carbon monoxide alarm legally required in the UK?
The answer depends on whether you own or rent, and which part of the UK you live in.
If you rent in England: Under the Smoke and Carbon Monoxide Alarm (England) Regulations 2022, your landlord is required by law to install a CO alarm in every room that contains a fixed combustion appliance. That includes gas boilers, gas fires, oil boilers, and solid fuel appliances such as log burners and open fires. It does not currently include gas cookers, though that guidance may change. CO alarms must be in working order at the start of each tenancy. If yours is missing or not working, contact your landlord in writing — they are legally obliged to provide it.
If you rent in Scotland: The Housing (Scotland) Act 2014, along with the First-tier Tribunal system, places similar obligations on landlords. Scotland requires interlinked alarms in most properties.
If you rent in Wales: The Renting Homes (Wales) Act 2016 requires landlords to provide working CO alarms in relevant rooms.
If you rent in Northern Ireland: There is no equivalent statutory requirement at present, though this may change. Your tenancy agreement may specify alarm requirements separately.
If you own your home: There is no legal requirement to fit a CO alarm. But the advice from every UK Fire and Rescue Service, the NHS, and Gas Safe Register is unambiguous: fit one if you have any gas, oil, or solid fuel appliance. Carbon monoxide poisoning is responsible for around 40–50 accidental deaths per year in England and Wales. It is entirely preventable with a £20 alarm.
If you rent and your landlord has not fitted a CO alarm in a room with a fuel-burning appliance, send a written request (email is fine). Keep a copy. If they fail to act, local councils have the power to issue remedial notices and fines of up to £5,000.
What most people get wrong
Confusing CO alarms with smoke alarms. They look similar and are often sold together, but they detect completely different things. Smoke alarms detect particles from burning material — fires. CO alarms detect carbon monoxide gas, which is produced by incomplete combustion in appliances that are working but not burning fuel cleanly. You need both. Having a smoke alarm does not protect you from CO poisoning, and vice versa.
Thinking only gas appliances produce CO. Carbon monoxide is produced by any fuel-burning appliance when combustion is incomplete — that includes gas boilers, gas fires, oil boilers, wood-burning stoves, open fires, and even portable gas heaters and barbecues. Electric appliances do not produce CO. If every appliance in your home is electric (including heating), you have no CO risk and no legal requirement.
Not knowing where to put it. Many people either mount the alarm directly beside the appliance (unnecessary and can cause false readings) or put it in an entirely different room (where it may not detect a slow-developing leak in time). The correct placement is in the same room, at head height, away from direct heat sources and cooking areas. More on this below.
Assuming the battery is what expires. CO alarms have electrochemical sensors that degrade over time. The sensor lifespan — typically 7–10 years — is the meaningful expiry date. When the sensor dies, the alarm can look fine and may even beep as if functioning, but it will not detect CO. Always check the manufacturer's printed expiry date on the unit, not just the battery status.
Where to place a CO alarm
CO (carbon monoxide) is approximately the same density as air — it does not sink to the floor like propane, and it does not rise sharply to the ceiling like hot smoke. This means placement is more flexible than with smoke alarms, but there are still clear guidelines.
Where to put it:
- In the same room as any fixed fuel-burning appliance — this is the primary location. A room with a gas boiler, gas fire, or log burner should have a CO alarm.
- At roughly head height — between 1 and 1.5 metres from the floor is fine. A wall mount, shelf, or bedside table all work.
- In any bedroom that is adjacent to a room with an appliance, particularly if you sleep with the door closed.
- If you have a garage with a car or petrol-powered tools, a CO alarm in the adjoining room or hallway is worth considering.
Where not to put it:
- Not in the kitchen. Gas hobs produce small amounts of CO during normal use, and the alarm will trigger false alarms while you're cooking. A CO alarm in a kitchen is more likely to make you disable it than to protect you.
- Not directly above or immediately beside the appliance. The British Standards guidance is to place it at least 1–3 metres from the appliance. Right next to the boiler can cause nuisance alarms from normal operation.
- Not in damp or very humid areas — bathrooms, for example. Moisture can damage the sensor over time.
- Not high on the ceiling like a smoke alarm. CO disperses through the room rather than rising, so ceiling placement offers no advantage and makes testing and battery replacement harder.
| Situation | Where to place |
|---|---|
| Gas boiler in a utility room | Inside the utility room, on a wall at head height |
| Gas fire in a living room | In the living room, 1–3m from the fire |
| Wood burner in a sitting room | In the sitting room, 1–3m from the stove |
| Boiler in a cupboard off a hallway | Inside the cupboard, or in the hallway immediately outside |
| Sleeping near an appliance room | In the bedroom, or on the landing between |
What you actually need
For most homes with one or two fuel-burning appliances, a single standalone CO alarm is enough. You do not need a hard-wired system, and you do not need an interconnected network of alarms unless you have an unusually large property with appliances in multiple zones.
What to look for in a CO alarm:
- EN 50291 certification — the European standard for CO alarms. Any alarm sold in the UK for domestic use should meet this standard. Don't buy one that doesn't list it.
- Long battery life or sealed battery — annual battery replacement is easy to forget. A 10-year sealed battery that matches the sensor lifespan is much more practical.
- Digital display (optional but useful) — shows CO concentration in parts per million (ppm). Useful for understanding whether a low-level reading is a brief spike or a sustained problem.
- Audible alarm — obvious, but ensure the alarm is loud enough to wake you from sleep if it's in or near a bedroom.
- Clear end-of-life indicator — the alarm should tell you when the sensor has expired, not just when the battery is low.
If you also need a smoke alarm, a bundle that includes both — with separate, independent sensors for each — can be a sensible purchase for a first home. Avoid combination units where a single sensor tries to detect both CO and smoke; they tend to compromise on both.
Best options by situation
For most homes
FireAngel FA3322 Digital Carbon Monoxide Alarm (10-Year Battery)
A standalone CO alarm with a 10-year sealed battery, digital CO concentration display, EN 50291-1 certification, and end-of-life warning. No battery changes required for the life of the unit.
Why this one: The sealed 10-year battery is the key feature. It means the alarm is maintenance-free for a decade — no annual battery swap to forget, no low-battery chirp at 3am. The digital display shows CO levels in ppm, which is genuinely useful: it tells you whether a reading is a brief spike from a cold boiler start-up or a sustained leak that needs action. Solid build quality and clear certification. At ~£20–28, it's the sensible default for most households.
Trade-off: At the higher end of the price range for a standalone alarm. The digital display adds cost over basic models. If you need two alarms for separate rooms (e.g. a boiler room and a bedroom), you'll be spending ~£40–56 — at that point, consider the bundle below.
For budget-conscious buyers or a spare alarm
Kidde 5CO Carbon Monoxide Alarm Twin Pack
A twin pack of CO alarms with EN 50291 certification, audible alarm, and replaceable battery. Straightforward and reliable — two alarms for roughly the price of one premium unit.
Why this one: The twin pack gives you two certified CO alarms for ~£18–25 total, which is exceptional value if you need to cover two rooms. Kidde is a well-established fire safety brand and these alarms are solid, no-frills units. Good for landlords fitting out a property, or homeowners with an oil boiler and a separate log burner.
Trade-off: Replaceable battery rather than sealed — you'll need to change batteries periodically and remember to do so. No digital display; the alarm is either sounding or silent, with no indication of CO concentration level. Sensor lifespan is typically 7 years rather than 10, so check the expiry date on the unit.
For a first home needing both CO and smoke protection
FireAngel FA3820 CO Alarm + FA6620-R Smoke Alarm Bundle
A bundle pairing the FireAngel FA3820 CO alarm with the FA6620-R optical smoke alarm. Both units have separate, independent sensors — the CO alarm detects carbon monoxide, the smoke alarm detects combustion particles. Both are battery-powered standalone units.
Why this one: If you're setting up a first home and don't have either alarm in place, buying both together is simpler and slightly cheaper than buying separately. The independent sensors matter: these are not a single combined unit trying to do both jobs with one sensor. Each alarm does one job correctly. Good for renters who need to cover both legal requirements in a room with a fuel-burning appliance, or homeowners setting up from scratch.
Trade-off: The smoke alarm in the bundle is an optical type, which is well-suited to slow, smouldering fires but less sensitive to fast, flaming fires. For a kitchen, an ionisation or multi-sensor smoke alarm may be preferable — but kitchens should not have CO alarms anyway, so the bundle fits other rooms well. At ~£30–40, it's good value for two alarms, but if you already have adequate smoke alarms fitted, buy just the CO alarm separately.
What to skip
Skip these — they come up in searches but aren't worth buying:
- Combination smoke/CO alarms with a single shared sensor. These exist at various price points and sound convenient. The problem is that a single electrochemical sensor can't do both jobs well. You're trading detection accuracy for shelf space. Fit separate alarms with independent sensors.
- Very cheap, unbranded CO alarms without EN 50291 certification. If the listing doesn't clearly state EN 50291, don't buy it. The standard exists for a reason, and an alarm that hasn't been certified to it may not reliably detect CO at dangerous concentrations.
- CO alarms sold as "suitable for boats and caravans" for use in a house. These are often calibrated differently and may not meet domestic standards.
- Alarms over 10 years old that you've found somewhere. Even if they appear functional, the sensor will have degraded. A CO alarm past its expiry date is not reliable. Check the date on the back.
- Smart CO alarms with apps and connectivity unless you have a specific reason to need them. The fundamental job of a CO alarm is to make a loud noise when CO is present. Adding connectivity doesn't improve detection — it adds cost and failure points.
Simple buyer plan
- One appliance, one room to cover: FireAngel FA3322 (~£20–28). One alarm, 10-year battery, done.
- Two rooms to cover, budget matters: Kidde 5CO Twin Pack (~£18–25). Two certified alarms for less than the price of one premium unit.
- No alarms at all in a new home: FireAngel FA3820 bundle (~£30–40). Gets you a CO alarm and a smoke alarm together, both with independent sensors.
- Renting: check whether your landlord has already fitted one. If they have, you're covered. If not, ask them to — it's their legal obligation in England, Scotland, and Wales.
- Own your home with gas or oil heating: fit one near the boiler at minimum. The FA3322 is the easiest option.
- Own your home with a wood burner or open fire: fit one in that room. Same recommendation.
- All-electric home: no CO risk from appliances; no alarm required. A smoke alarm is still strongly advisable.
Final recommendation
The FireAngel FA3322 is the straightforward answer for most people. It's certified, maintenance-free for a decade, and shows you CO levels rather than just sounding when a threshold is hit. At ~£20–28 for a unit that genuinely lasts 10 years, it's not an expensive purchase.
If you need two alarms — a boiler room and a bedroom, for instance — the Kidde 5CO twin pack offers better value per alarm and both units will do the job correctly.
The main thing is to have one fitted and in the right location. Check the room: if there's a boiler, a gas fire, or a solid fuel burner in it, that room needs a CO alarm. Check the expiry date on any alarm already in the property. If it's past the printed date, replace it.
Carbon monoxide is not something to approach cautiously or defer until you've done more research. This is a £20 purchase. Make it.
Setting up a new home and not sure what else you need? Our first home essentials checklist covers the basics across safety, tools, and kitchen equipment.