Smoke Alarms and CO Detectors — What Changed in 2022 and What You Actually Need

Last month I carried out an EICR on a three-storey rental in Bishopthorpe Road. The electrics were in decent shape — no immediate concerns with the wiring or the consumer unit. But the property had a single ionisation smoke alarm on the landing, no alarm on the ground floor, and nothing at all for carbon monoxide. The gas boiler sat in the kitchen with no CO detector in sight.

That’s not unusual. Before October 2022, the legal requirements for smoke and CO alarms in rented properties were surprisingly thin. The law has changed, and the requirements are clearer now — but there’s still a lot of confusion about what’s actually needed, what type of alarm to buy, and when you need an electrician involved.

What Changed in October 2022

The Smoke and Carbon Monoxide Alarm (Amendment) Regulations 2022 updated the original 2015 rules. Before the amendment, landlords had to fit smoke alarms on each floor and CO alarms in rooms with solid fuel appliances (wood burners, coal fires) — but gas boilers and oil burners were not covered. The 2022 amendment closed that gap.

The penalty for non-compliance is a civil fine of up to £5,000. It’s enforced by local authorities, and while enforcement varies, the requirement itself is not optional.

What About Owner-Occupiers?

There is no legal requirement for owner-occupiers to fit smoke alarms or CO detectors in England. That surprises a lot of people. The regulations apply exclusively to rented properties — both social housing and private rentals.

That said, the fire service recommendation is clear: every home should have working smoke alarms on each floor and CO alarms near any fuel-burning appliance. BS 5839-6 — the British Standard for fire detection in residential properties — sets out detailed guidance on alarm type, placement, and system design. I follow that standard on every installation, whether the property is rented or owner-occupied.

Ionisation vs Optical Alarms — Which Type Do You Need?

This is where a lot of people get caught out. There are two main types of smoke alarm, and they detect different kinds of fire.

Ionisation alarms contain a small amount of radioactive material that ionises the air inside a sensing chamber. When smoke particles enter the chamber, they disrupt the current and trigger the alarm. These are very responsive to fast-flaming fires — a chip pan catching, paper igniting — but they are also notoriously prone to false alarms from cooking fumes, steam, and even dust. That’s why people take them down or remove the battery. Once that happens, the alarm is useless.

Optical alarms (also called photoelectric alarms) use a light beam inside the sensing chamber. When smoke particles scatter the beam, the alarm triggers. These are better at detecting slow-smouldering fires — an overheating appliance, a cigarette igniting a sofa — and they produce far fewer false alarms near kitchens and bathrooms.

For most homes, I recommend optical alarms. They are what BS 5839-6 recommends for escape routes, and they stay on the ceiling where they belong because people are not constantly battling false alarms. In kitchens, neither type is ideal — a heat alarm is the better option. Heat alarms trigger on temperature rather than smoke particles, so cooking does not set them off.

Where Do Alarms Need to Go?

The regulation says “every storey with living accommodation” for smoke alarms, but that’s the legal minimum. BS 5839-6 goes further with its grading system. For a typical two-storey house, here is what I recommend as a practical minimum:

In a three-storey property or a house with a loft conversion, the number of alarms increases accordingly. Every habitable floor needs coverage. I see this missed regularly on EICRs — the loft bedroom has been signed off by building control, but nobody fitted a smoke alarm up there.

Interlinked and Hardwired Systems vs Battery Units

The 2022 regulations do not specify that alarms must be hardwired or interlinked. A £6 battery-operated smoke alarm from the supermarket is technically compliant for a rented property. But “compliant” and “properly protected” are not the same thing.

Standalone battery alarms do one job: they sound in the room where they detect smoke. If you are asleep two floors up with the bedroom door closed, you may not hear a standalone alarm going off in the hallway downstairs. That is the scenario where people die in house fires.

Interlinked alarms solve this. When one alarm detects smoke, heat, or CO, every alarm in the system sounds simultaneously. You hear the alarm no matter where you are in the house. Interlinked systems come in two forms:

Radio-frequency (RF) interlinked battery alarms communicate wirelessly. They are a significant step up from standalone units and do not require any wiring work. They are a good option for owner-occupiers who want better protection without the cost of a hardwired system, and for landlords upgrading rental properties without major disruption.

Hardwired mains-powered interlinked alarms are permanently wired into the property’s electrical installation on a dedicated circuit. They have battery backup so they continue to work during a power cut. This is the gold standard — it is what BS 5839-6 recommends, what building regulations require on new builds and major renovations, and what I fit when the opportunity is there.

Installing a hardwired fire alarm circuit in a domestic property is notifiable work under Part P of the Building Regulations. That means it needs to be carried out by a registered electrician or inspected by building control. If I am already carrying out a consumer unit upgrade, adding hardwired smoke and CO detection at the same time is straightforward — the ceiling access is already open, the circuit can be wired directly from the new board, and the additional cost is modest compared to doing it as a separate job.

When You Need an Electrician vs When You Can DIY

This is genuinely simple:

If you are a landlord trying to decide which route to take, here is my honest recommendation: RF interlinked battery alarms are the minimum I would consider acceptable. They cost more than standalone units — typically £25–£40 per alarm head — but they give your tenants genuine protection across the whole property. If you are planning any electrical work on the property anyway — an EICR, a board upgrade, additional circuits — ask about adding hardwired detection at the same time. The incremental cost is much lower when the infrastructure work is already happening.

What I See on EICRs

Smoke and CO detection comes up on almost every EICR I carry out. The most common observations are:

No smoke alarm on every floor. Typically the ground floor gets missed. The property has an alarm upstairs on the landing but nothing in the downstairs hallway.

Ionisation alarms with the battery removed. The alarm was too close to the kitchen, it kept going off during cooking, and eventually someone took the battery out. Now it is just a plastic disc on the ceiling doing nothing.

No CO alarm near the boiler. Before the 2022 amendment, this was not a legal requirement for gas appliances. A lot of properties still have not caught up.

Alarms past their replacement date. Smoke alarms have a lifespan of around 10 years. CO alarms typically last 5–7 years. Both have an expiry date printed on the unit. I check this during every inspection, and a surprising number are well past their service life.

These are recorded as observations or recommendations on the EICR. They do not automatically fail the report, but they are flagged for the property owner to address. For landlords, ignoring smoke and CO alarm recommendations on an EICR is a risk — both legally and in terms of tenant safety.

For Larger Properties and Commercial Installations

Everything above applies to standard domestic properties. If you manage a commercial building, an HMO, or a property that needs a full fire detection system designed to BS 5839-1 (the commercial fire detection standard), the requirements are more involved. System design, zoning, control panels, and regular maintenance contracts all come into play. That is a different conversation — but I handle those installations as well.

Frankie Sewell
NICEIC Approved Contractor • YRLA Recognised Service Provider • Bright Sparks of York