Carbon monoxide (CO) is known as the silent killer. You can’t see it, smell it, or taste it, and yet it kills people every year in the UK.
What’s scary is how easily it can happen: a blocked flue, a poorly ventilated gas appliance, or even a solid fuel stove running too long.
That’s why carbon monoxide alarms aren’t just a smart precaution anymore, they’re a legal requirement in most UK homes under the 2022 regulations.
But here’s the question most homeowners get wrong: where do these alarms go? You might think one in the hallway will do, but that’s not always enough or even compliant. Let’s get this right, from what the law says to how professionals do it for maximum protection.
What The 2022 Carbon Monoxide Regulations Actually Say
Updated October 2022, the rules now require CO alarms in any room in England that contains a fixed combustion appliance.
That means:
- Landlords must fit alarms in every relevant room.
- Homeowners are advised (and in some areas required) to do the same.
- Alarms must be British Standard BS EN 50291 and have a Kitemark or equivalent approval.
A few things often overlooked:
- Portable gas heaters are also combustion appliances.
- Cookers are exempt unless they’re in a room with a sleeping area, but many experts recommend covering kitchens anyway.
And here’s a key point for landlords:
When a tenant reports a faulty or expired CO alarm, you must replace it immediately. Failure to do so could lead to enforcement action from the local council.
Why Correct Placement Matters More Than Most Think?
Installing an alarm is easy, but installing it wrong can make it almost useless.
Carbon monoxide is roughly the same density as air, so it disperses evenly in a space. But temperature, air movement, and the layout of the room all affect how quickly it reaches the alarm.
Mount it too close to the appliance, and it will trigger false alarms. Too far away, and it might not catch a leak until the levels are too high.
Professional installers talk about the “three-foot rule”: Keep CO alarms at least 1–3 feet from the appliance and at head height, ideally the same level as you breathe when in the room.
If the alarm is on the ceiling, keep it at least 300mm from any wall or light fitting, the same as smoke alarms, but with more flexibility.
Room-By-Room Guide: Where Carbon Monoxide Alarms Should Go
Let’s get practical. Here’s how professionals place alarms in different areas of a UK home:
1. Boiler Rooms And Utility Areas
Most gas boilers live here.
Mount the alarm on the wall, 1–3 metres from the boiler. If the boiler’s in a cupboard, don’t put the alarm inside, instead, just outside the door where airflow reaches.
Avoid corners or areas with strong drafts. A gentle cross-ventilation path is best for accuracy.
2. Living Rooms With Fires Or Log Burners
These are high-risk spaces, especially with solid fuel stoves.
Fit the alarm at head height when seated, often on a side wall near the fireplace, but not above it.
Remember, CO can travel between floors, so if you’ve got an open-plan space or mezzanine, consider another alarm upstairs.
3. Bedrooms
You sleep for hours without awareness.
That’s why the alarm should be at breathing level, 1–1.5 metres from the bed, or on the wall just above skirting height.
If there’s a boiler or heater in an en-suite, it needs its own dedicated alarm.
4. Kitchens
Not required by law in most cases, but let’s be real, a gas cooker is still a combustion source.
Install a CO alarm at least one metre away from hobs or ovens, ideally near the entrance or along a side wall.
Avoid steam-heavy zones, as moisture can trigger false readings.
5. Hallways And Landings
These are often the “link” areas where CO can spread unnoticed.
Position one here, especially between sleeping areas, is a good move, especially in multi-floor homes.
Common Mistakes And (How Pros Avoid Them)
Even when people buy good-quality alarms, they sometimes install them in a way that defeats the purpose. Here are a few of the classic mistakes:
- Place them next to the appliance: The gases haven’t cooled or dispersed yet, so readings are unreliable.
- Mounting them too high above normal airflow: CO mixes evenly, so positioning matters. Being too close to the ceiling can delay detection.
- Hiding them behind curtains or furniture: Looks neater, yes, but airflow drops drastically.
- Ignoring the expiry date: CO sensors degrade. Most alarms have a 5–7 year lifespan. Always check the “replace by” date on the back.
- Using the wrong type of alarm: A cheap “plug-in” designed for caravans isn’t ideal for a large living room. Mains powered with battery backup is the best long-term protection.
And one more thing, never combine CO and smoke sensors in one spot unless the manufacturer says you can.
CO and smoke behave differently, so a “combo” alarm must be specifically designed for both gases.
Visual Vs Audible: Which Type Of Alarm Works Best?
No rule says you can’t have both. In fact, the best systems use a mix.
- Audible alarms (the standard kind) are vital, they wake you up, which could save your life.
- Visual indicators, like red or green LED status lights, are great for routine checks but shouldn’t be relied on alone.
For those with hearing impairments, strobe lights or vibrating pads are available and fully compliant with UK safety standards.
The key is simple: whatever you choose, make sure it’s tested weekly and certified to BS EN 50291. That’s non-negotiable.
Maintaining And Testing Your CO Alarms
Even the best alarm is only as good as its maintenance. Once a month, press and hold the test button until it beeps, which confirms it’s powered and responsive. Replace batteries annually unless you’ve got a sealed, 10-year unit.
Wipe off dust, and avoid using cleaning sprays anywhere near the sensor vents.
If your alarm starts chirping intermittently (and not as a test alert), it’s likely signalling low battery or end-of-life.
Don’t ignore that sound, it’s not a glitch; it’s the device telling you it’s no longer reliable.
What “Competent Person” Means For Installation
Under UK guidance, CO alarms don’t always have to be installed by a professional. But in rented or managed properties, the landlord’s duty means they’re expected to use a competent person, someone trained or qualified to understand placement and compliance.
That could mean a Gas Safe engineer, an electrician, or a certified fire safety contractor.
DIY is fine in owner-occupied homes, but when in doubt, professional fitting ensures no mistakes in distance, airflow, or power supply, especially if connecting alarms in a linked system.
The Role Of Smart Alarms
The last few years have seen a big shift to smart CO alarms, ones that connect via Wi-Fi or Bluetooth to apps. These can send alerts directly to your phone if levels rise, even when you’re away.
For landlords or property managers, this is especially useful, allowing remote checks on multiple properties.
Just remember: even with tech upgrades, regular physical testing is still essential. No system replaces human oversight entirely.
A Tool Worth Mentioning: Tradefox
If you’re in the trade, whether as a gas engineer, electrician, or building inspector, you’ll know that practice is everything.
That’s where tools like Tradefox come in handy.
It’s a simulation app designed for UK tradespeople to train safely, test scenarios like CO leak responses, and sharpen decision-making without risking real-world hazards.
For new apprentices or self-employed pros keeping up with compliance, it’s worth a look.
Final Thoughts
A carbon monoxide alarm isn’t something you buy once and forget. It’s part of your home’s safety ecosystem as vital as a smoke alarm or RCD-protected consumer unit.
The 2022 regulations made the message clearer than ever: every room with a combustion appliance needs a CO alarm.
But beyond the legal side, there’s a practical one, peace of mind.
Positioned properly, maintained regularly, and installed by someone who knows the rules, a small device can prevent the unthinkable.
Simple, silent, and lifesaving.
