Carbon Monoxide Alarm Regulations: What Landlords Must Provide
Carbon monoxide alarm regulations for landlords have tightened significantly in recent years, and most Middlesbrough rental property owners are either confused about what they actually require or quietly unsure if they're compliant. The fear is understandable — carbon monoxide is invisible, odourless, and genuinely lethal. According to the HSE, accidental carbon monoxide poisoning causes around 60 deaths and thousands of hospital admissions in the UK every year. In rental properties, where tenants rely on the landlord to maintain gas appliances and heating systems, the risk is real.
For landlords managing properties across TS1, TS3, TS5, and TS7, the legal obligation is clear: if there's a fixed combustion appliance (gas boiler, gas fire, oil heater, solid fuel stove), there must be a carbon monoxide alarm in that room. Getting this wrong isn't a minor paperwork slip — it's a compliance breach that triggers £5,000 fines from local authorities. More importantly, it's a genuine safety gap that could hurt a tenant living in your property.
Here's exactly what the regulations require, what to install, and the mistakes to avoid.
Why Carbon Monoxide Alarms Matter
Carbon monoxide (CO) is produced whenever any fuel burns — gas, oil, coal, wood, or even charcoal. In a well-maintained property with properly functioning appliances, CO levels stay safe. But when an appliance malfunctions, is poorly installed, or isn't serviced, CO can accumulate quickly in the room where it's burning.
The danger is that CO is impossible to detect without an alarm. You can't see it, smell it, or taste it. Early symptoms — headache, dizziness, nausea — are easily mistaken for flu. By the time a tenant realizes something is wrong, they may already be at serious risk.
This is why the regulations exist and why they've been strengthened. Since the Smoke and Carbon Monoxide Alarm (Amendment) Regulations 2022 expanded the requirements, CO alarms are now mandatory in any room containing a fixed combustion appliance. This includes gas boilers (the most common requirement in Middlesbrough terraces and semis), gas fires, oil-fired heaters, and solid fuel burners.
What the Regulations Actually Require
The legal requirement is straightforward: a carbon monoxide alarm must be installed in any room containing a fixed combustion appliance.
For a typical Middlesbrough rental property, this usually means:
- Gas boiler in the kitchen? You need a CO alarm in the kitchen.
- Gas fire in the living room? CO alarm in the living room.
- Boiler in a utility room or airing cupboard? Alarm in that space.
- Oil-fired heating or solid fuel stove? Same rule applies.
The key change in 2022 was the inclusion of gas appliances. Before the amendment, landlords with only gas boilers could legally have no CO alarms at all. That's no longer the case.
The regulations also require that alarms comply with British Standard EN 50291. When you buy an alarm, check the packaging — the standard should be clearly marked.
Beyond installation, you must ensure alarms are in working order at the start of each new tenancy. This means physically testing them — pressing the test button and confirming the alarm sounds — during check-in. As part of staying compliant with changing letting regulations, ongoing testing during routine inspections is best practice.
The Right Alarm Type and Installation
You have two main options: battery-powered or mains-wired alarms. Both are compliant as long as they meet EN 50291.
Battery-powered alarms are the simplest and cheapest option, typically costing £15–£25 each. Look for sealed lithium battery units with a ten-year lifespan — they require no battery changes during their lifetime and provide reliable protection. Avoid cheap alarms with replaceable AA batteries, which tenants may remove and forget to replace (you discover this the hard way when the alarm doesn't work during an inspection).
Mains-wired alarms are wired into the property's electrical system, usually with battery backup. Installation typically costs £60–£100 per unit including an electrician. If you're renovating a property or having electrical work done anyway, mains-wired alarms are worth considering for the peace of mind. For most landlords with smaller portfolios, sealed battery alarms are sufficient and more cost-effective.
Positioning matters. Carbon monoxide mixes evenly with air — it doesn't rise or fall like smoke — so alarms can be wall-mounted at head height (approximately 1.5 metres from the floor) or ceiling-mounted. Always follow the manufacturer's instructions. Position the alarm 1–3 metres from the appliance where possible, but not directly above or next to it (heat and steam can cause false alarms).
Avoid bathrooms, windows, doors (drafts interfere with detection), directly above cooking hobs, and enclosed spaces with poor air circulation.
If your property has multiple combustion appliances in different rooms — for example, a gas boiler in the kitchen and a gas fire in the living room — you need separate alarms in each room. This is a common gap in Middlesbrough terraces with original fireplaces plus central heating.
Testing, Maintenance, and Expiry
The HSE requires landlords to ensure CO alarms are in proper working order at the start of each new tenancy. Physically test the alarm on move-in day. For existing tenancies, best practice is to check all CO alarms during routine property inspections, which should happen at least every six months (and which we recommend quarterly or at minimum biannually).
If a tenant reports a non-functional alarm, replace it promptly. A broken alarm is the same as no alarm.
CO alarms have a limited lifespan — typically 7–10 years depending on the model. Check the expiry date printed on the alarm and replace it before that date expires. An expired alarm may not detect CO reliably, even if the test button still sounds. The sensor degrades over time.
Adding CO alarm replacement dates to your compliance calendar ensures nothing slips through. Many landlords keep a simple spreadsheet: property address, alarm make/model, installation date, expiry date, test result. This documentation also protects you if a local authority inspection happens or if a problem arises.
Penalties and Common Mistakes
Local authorities have significant enforcement power. They can issue a remedial notice requiring you to install CO alarms within 28 days. If you don't comply, the council can install them themselves and charge you for the cost — plus issue a civil penalty up to £5,000.
Middlesbrough and the wider Teesside area have increased enforcement activity in recent years. Properties inspected as part of HMO licensing applications, Right to Rent checks, or complaint investigations are routinely checked for CO alarm compliance. This is also where the most common mistakes surface:
Installing alarms in hallways instead of the appliance room. The alarm must be in the same room as the combustion appliance. A hallway alarm when the boiler is in the kitchen does not meet the requirement.
Relying on annual gas safety checks as a substitute. A Gas Safety Certificate confirms appliances are safe at inspection. It doesn't protect against faults that develop between inspections. CO alarms provide continuous monitoring — they're a separate requirement, not an alternative.
Forgetting about boilers in bedrooms. Some older Middlesbrough terraces have boilers in airing cupboards within or opening onto bedrooms. If the boiler is in or next to a bedroom, that room needs a CO alarm. This is surprisingly common in older properties where space was at a premium.
Not checking expiry dates. An expired alarm may appear to work when tested, but the sensor has degraded. It's not compliant, and it won't reliably detect CO.
Assuming tenants will sort it. The legal obligation sits with you, the landlord. You cannot delegate this by asking tenants to buy their own alarms. You must provide them, test them, maintain them, and replace them.
As with other compliance rules that changed in 2025, the details matter. A half-hearted approach — an alarm in the wrong room, an expired alarm left in place, or no alarms at all — creates both a legal exposure and a genuine safety gap.
Frequently Asked Questions
Q: Do I need a carbon monoxide alarm if I have an electric boiler?
A: No. Electric boilers do not produce carbon monoxide because they don't burn fuel. CO alarms are only required for combustion appliances (gas, oil, solid fuel). If you're unsure what type of boiler you have, check the boiler itself or ask your gas engineer during the annual safety check.
Q: My property has a gas fire that hasn't been used in years. Do I still need an alarm?
A: Yes. The regulation applies to any fixed combustion appliance, whether it's currently in use or not. If the gas fire is still connected to the gas supply, you need a CO alarm in that room. If you've permanently disconnected it and capped off the gas supply, you may not need the alarm — but get confirmation from a Gas Safe engineer.
Q: Can I use a combined smoke and CO alarm?
A: No. While combined alarms exist for consumer use, the regulations require separate smoke and CO alarms. You must have a smoke alarm on every storey and a CO alarm in every room with a combustion appliance. They're two distinct legal requirements.
Q: What happens if a tenant damages or removes a CO alarm?
A: Document it immediately. Take photos, record the date, and notify the tenant in writing that the alarm must be replaced at their expense (or explain that removal of a safety device may be grounds for disciplinary action). However, you remain legally responsible for ensuring a working alarm is in place — if the tenant refuses to cooperate, you may need to arrange replacement yourself and deduct the cost from the deposit (within legitimate dispute resolution), or address it as a breach of tenancy terms. This is one of the situations where understanding letting regulations penalties is essential.
Q: How often should I test the alarms myself?
A: At minimum, test all CO alarms when a new tenant moves in and during any routine property inspection. We recommend quarterly or biannual inspections. The tenant can test the alarm monthly themselves by pressing the test button, but the legal responsibility for ensuring the alarm works rests with you. Keep records of your tests.
Q: If I use a letting agent, who's responsible for CO alarms?
A: The legal responsibility is always the landlord's. However, a good agent (like Ascot Knight) will handle installation, testing, maintenance, and replacement as part of the management service. Always confirm in writing that your agent is responsible for CO alarm compliance and that they'll provide evidence (photos, test records, replacement receipts). If you're managing the property yourself, you must handle all of this directly.
Q: What's the difference between a CO alarm and a CO detector?
A: In practice, no meaningful difference. "Alarm" and "detector" are used interchangeably. Both refer to a device that monitors CO levels and sounds an audible alarm when CO reaches dangerous levels. Ensure whatever you buy meets EN 50291.
Q: Do I need CO alarms in a flat or apartment?
A: Yes, if the flat has its own fixed combustion appliance (boiler, fire, heater). If the building has a communal boiler serving multiple flats, the alarm requirement depends on whether the tenant has access to the boiler room and whether CO could enter the flat from it. Consult the HSE guidance or a gas engineer for your specific setup — flat buildings can have complex configurations.
Next Steps
The total cost of CO alarm compliance — a sealed ten-year battery alarm in each room with a combustion appliance, typically one or two per property — is £20–£50 per property. The cost of non-compliance — in fines, legal liability, and human terms — is immeasurably higher.
If you're unsure whether your Middlesbrough rental property meets current CO alarm regulations, contact Ascot Knight for a free compliance check. We'll ensure every property is correctly equipped, tested, and documented. As part of our property management service, CO alarm compliance is built in — one less thing to worry about.