Interlinked smoke alarms all sound together: when one detects smoke, every alarm in the house goes off, not just the one in the room with the fire.
That difference matters most at three in the morning, when the fire is in the kitchen and you are asleep two floors up.
Interlinking used to be a nice-to-have. It is now a legal requirement in some UK homes and strongly recommended in the rest, and the wireless versions have made retrofitting it a morning's work rather than a rewire.
Here is what you need, where it goes, and which bits people get wrong.
1. What "interlinked" actually means
A standalone alarm protects the room it is in. If it sounds and nobody is in earshot, it has done its job and achieved nothing.
Interlinked alarms talk to each other. One triggers, all sound. The point is not louder noise — it is that the warning reaches the person furthest from the fire, which is usually the person asleep.
There are two ways to achieve it: a wired interconnect between mains alarms, or a radio-frequency link between alarms that pair wirelessly. Both are legitimate. They suit different buildings.
2. Do you actually need them?
Requirements differ across the UK and change over time — confirm the current position for your property and tenure before you rely on this.
Scotland has the strictest standard: since February 2022 every home, owned or rented, has been required to have interlinked alarms — smoke alarms in the main living area and circulation spaces on every storey, a heat alarm in the kitchen, and a carbon monoxide alarm where there is a fuel-burning appliance.
England requires, in rented homes, at least one smoke alarm on every storey used as living accommodation, plus a carbon monoxide alarm in any room with a fixed combustion appliance other than a gas cooker. Interlinking is not mandated for existing rented stock in the way it is in Scotland, but building regulations push new and materially altered homes toward it.
Wales requires rented homes to have mains-wired, interlinked smoke alarms on each storey as part of the fitness standard.
If you own your home in England or Wales, you are largely in "strongly recommended" territory rather than "legally required". The fire service recommendation has been consistent for years, and it is the same advice we give across the counter: interlink it anyway.
Trade Tip: if you are a landlord, photograph every alarm on the day of installation with the test button pressed and the date visible on your phone. Compliance disputes are won with records, and "there was definitely one there" is not a record.
3. Hard-wired or RF — which interlink to choose
Hard-wired interlink runs a three-core-and-earth interconnect between mains alarms. It is the belt-and-braces answer, it needs no pairing, and it is the obvious choice when you already have the ceilings open — a rewire, a refurbishment, a new build.
RF interlink pairs alarms over radio. No interconnect cable, so no chasing, no lifting floorboards, no making good. In an occupied house with plastered ceilings this is usually the sensible answer, and the alarms themselves can still be mains-powered with battery backup.
Take a stance? For a retrofit in a lived-in home, RF, every time. The cable route is the expensive part of the job and RF deletes it.
Aico Ei3000MRF SmartLINK Module — Wireless Interconnection for 3000 Series. This is the part that turns a set of 3000-series alarms into an interlinked system without an interconnect cable. Worth understanding before you buy the alarms themselves, because it decides which base you want.
4. Which alarm goes in which room
The commonest mistake in the whole subject is putting a smoke alarm in the kitchen. It will detect toast, you will get fed up, and within a fortnight it will be in a drawer. Kitchens take a heat alarm, which responds to temperature rise rather than smoke.
As a working layout for a typical two-storey house: smoke alarms in the hallway and on the landing, a heat alarm in the kitchen, and a carbon monoxide alarm wherever there is a boiler, stove or fire.
Aico Ei3016 Optical Smoke Alarm — High-Performance Sensor, Ei3000MRF Compatible. The hallway-and-landing alarm. Optical sensing suits circulation spaces, and its compatibility with the Ei3000MRF module is what lets it join a wireless interlinked system.
Aico Ei3014 Heat Alarm — High-Performance Thermistor Sensor, Ei3000MRF Compatible. The kitchen alarm. Thermistor sensing means it reacts to heat, not to whatever you have just burnt, and it interlinks with the same module as the smoke alarms.
Aico Ei3028 Multi-Sensor Heat & Carbon Monoxide Alarm — Dual Sensor Protection. One device covering both heat and CO, which is useful where a kitchen also holds the boiler and you would rather not fit two units to one ceiling.
For siting detail — heights, distances from walls, which rooms genuinely need one — read where to place a carbon monoxide detector, and compare specific models in the best smoke and CO detectors.
5. Mains-powered or 10-year battery?
Mains alarms with a battery backup are the standard for rented and new-build work, and they are what a wired interlink assumes. In BS 5839-6 language this is the Grade D territory that most domestic specifications land in — your installer will tell you which grade and coverage category your property needs.
Sealed 10-year lithium alarms need no mains supply and no annual battery change, which makes them the practical answer for an owner-occupier retrofit where nobody is lifting a floorboard.
Aico Ei650i Battery Optical Smoke Alarm — 10-Year Lithium, AudioLINK+. No mains, no annual battery swap, and AudioLINK+ for reading data off the alarm. The straightforward choice where running a supply is not on the cards.
Trade Tip: whichever you fit, press the test button on every alarm once a month and do it from the furthest bedroom with the doors shut. Testing an alarm while standing underneath it proves the sounder works. It does not prove you would hear it asleep, which is the only test that matters.
Summary: interlinked smoke alarm quick reference
| Location | Alarm type | Why |
|---|---|---|
| Hallway, landing, circulation | Optical smoke | Catches smoke on the escape route |
| Kitchen | Heat | Ignores cooking, reacts to temperature rise |
| Boiler, stove or open fire | Carbon monoxide | CO is odourless — no alarm, no warning |
| Existing house, ceilings closed | RF interlink | No interconnect cable, no making good |
| Rewire or new build | Hard-wired interlink | Ceilings already open, nothing to pair |
Expert Help in the West Midlands
We have supplied alarms from our Villa Road counter in Birmingham since 1975, to landlords doing a portfolio and to homeowners doing one hallway. Bring a rough sketch of your floor plan — rooms, storeys, where the boiler is — and we will tell you what the system needs and, more usefully, what it does not.
Browse smoke alarms and detectors, heat alarms, smart and wireless smoke alarms and the wider fire and safety equipment range.
Interlinked smoke alarm FAQs
Do interlinked smoke alarms have to be hard-wired?
No. Radio-frequency interlink achieves the same result without an interconnect cable, and the alarms can still be mains-powered with battery backup. Check your own requirement — Scotland's rules and the rented-sector rules in England and Wales differ, and a landlord's obligations are not the same as an owner-occupier's.
How many interlinked smoke alarms do I need?
As a working minimum for a two-storey house: one on each storey in the hallway or landing, a heat alarm in the kitchen, and a CO alarm by any fuel-burning appliance. Larger or multi-let properties need a proper assessment rather than a rule of thumb.
Can I mix brands in one interlinked system?
Treat that as a no. Interlink is brand-specific and often range-specific — a wireless module made for one series will not pair with another manufacturer's alarms. Pick one range and stay in it, and check compatibility on the module rather than assuming it.