An interlinked alarm is a smoke, heat or carbon monoxide alarm that's connected to every other alarm in a property, so that when one alarm detects danger, they all sound together.
If a fire starts in the kitchen while you're asleep upstairs, an interlinked system means the alarm outside your bedroom can go off at the same time as the one in the kitchen, rather than relying on smoke reaching another alarm elsewhere in the house.
A single, isolated alarm can only warn the people close enough to hear it. An interlinked system turns every alarm in the home into part of one early warning network, which is why interlinked alarms are recommended as part of fire safety guidance and are a legal requirement for many types of properties across the UK.
How Do Interlinked Alarms Work?
Interlinked alarms communicate with each other so that when one alarm activates, the other alarms in the system also sound. There are two main ways this connection can be made: radio frequency (RF) or a physical interlink connection.
It's important to distinguish between how an alarm is powered and how it interlinks. An alarm can be battery powered and RF interlinked, or it can be mains powered and RF interlinked. A mains-powered alarm still requires an appropriate electrical connection even when the alarms communicate wirelessly.
| Interlink type | How it works |
|---|---|
| Radio frequency (RF) interlink | Alarms communicate wirelessly with each other. When one detects danger, it sends an RF signal to the other paired alarms, which then sound according to the system's specifications. |
| Wired interlink | Alarms communicate through a physical interlink connection. This can be used alongside a mains electrical connection, depending on the alarm and installation. |
Wireless (Radio Frequency) Interlinked Alarms
Wireless interlinked alarms communicate using radio frequency (RF) signals, rather than WiFi or Bluetooth.
Each alarm has a radio transmitter built in. When one alarm detects smoke, heat or carbon monoxide, it sends an RF signal to the other paired alarms in the system, causing them to sound.
RF describes how the alarms communicate, not how they are powered. Battery-powered alarms can use RF to interlink, but mains-powered alarms can also use RF. Mains-powered RF alarms still require the appropriate electrical installation, even though no physical interlink cable is needed.
Because battery-powered RF alarms don't require fixed electrical wiring, they can be a practical option for existing homes, rental properties and anywhere installing new mains cabling would be disruptive.
All LINKD wireless alarms come with their own RF transmitter. With some other brands, an additional module or compatible unit may be required to enable RF interlinking, which can increase the overall cost.
Mains-Powered Interlinked Alarms
Mains-powered alarms receive their primary power from the property's electrical supply, usually with a battery back-up.
Mains-powered does not necessarily mean the alarms are physically wired together. Mains-powered alarms can communicate with each other wirelessly using RF, meaning the power connection is wired but the interlinking is wireless.
Where a physical interlink connection is used, the alarms are connected as part of the electrical installation. Installing new mains-powered alarms or physical interlink cabling involves electrical work and should be carried out in accordance with the applicable requirements.
Many existing homes and rental properties use wireless interlinking, including installations where mains-powered alarms are required.
Interlinked vs Standalone Alarms
A standalone alarm works entirely on its own. It monitors the room it's fitted in and sounds when it detects smoke, heat or carbon monoxide. If nobody is close enough to hear it, it won't raise the alarm elsewhere in the property.
An interlinked alarm removes that gap in coverage. When any alarm in the system is triggered, the other interconnected alarms also sound, regardless of which floor or room they're in.
Standalone alarms are cheaper to buy individually and simpler to install, which is why they're still found in some properties. But for homes where multiple alarms are required, interlinking provides a way to ensure an alarm activation is communicated throughout the property.
| Limitation of a standalone alarm | How an interlinked alarm solves it |
|---|---|
| Only sounds in the room it's fitted in | Every alarm in the system sounds together, wherever the danger is detected |
| May not be heard through a closed door | Interlinking means every alarm sounds, not just the nearest one |
| Limited protection in larger or multi-storey homes | Adding more interlinked alarms extends coverage |
| No warning if you're not close enough to hear it | You're alerted wherever you are in the property, day or night |
Why Interlinked Coverage is Important
One alarm sometimes isn't enough, and coverage is often the reason why.
Government fire statistics for England show that, in the year ending March 2025, fires where a smoke alarm was present but either did not operate or did not raise the alarm accounted for 29% of all dwelling fires.
Of the recorded reasons why an alarm failed to raise the alert, 48% were because the fire did not reach the detector, and 15% were because the fire was in an area not covered by the alarm system.
Combined, that's 63% of recorded reasons linked to the alarm not being close enough to the fire, or the fire starting outside the system's coverage area.
This is where interlinking can help. It's not just about having an alarm somewhere in the property. It's about making sure a detection anywhere in the system is communicated to the other alarms in the property, which is exactly what interlinking is designed to do.
Do Smoke Alarms Need to Be Interlinked in England?
This depends on the property and the requirements that apply to it.
Approved Document B sets out fire safety guidance for building work in England, including requirements relating to fire detection and alarm systems. Requirements can differ depending on whether you're dealing with a new dwelling, an existing property, an extension or a conversion.
Existing homes, including private rented properties, are governed differently. Landlords must fit at least one smoke alarm on every storey used as living accommodation, while additional requirements can apply depending on the property and local licensing conditions. You can check the current England compliance requirements in full here.
We recommend our customers also ensure they are aware of the requirements of their local council, so they know whether interlinked alarms are a legal requirement under their Selective or Additional Licensing Scheme.
Do Smoke Alarms in Rental Properties Have to Be Interlinked?
The answer changes depending on which UK nation the property is in.
If you own or manage rental properties in more than one nation, the safest approach is to understand the specific requirements applying to each property. Fitting interlinked alarms as standard can also provide a consistent approach across a portfolio, rather than tracking which properties technically need interlinking and which don't.
| Nation | Requirement |
|---|---|
| England | At least one smoke alarm per storey with living accommodation. Interlinking is recommended and can be a legal requirement under some local licensing schemes. |
| Wales | Since 1st December 2022, private and social rented homes have specific requirements for mains-powered, interlinked smoke alarms, with at least one on every storey. |
| Scotland | Since 1st February 2022, every home must have interlinked smoke alarms in the main living area and every circulation space, with additional requirements for kitchens and carbon monoxide alarms depending on the circumstances. |
| Northern Ireland | Private rented properties are subject to specific requirements for smoke, heat and carbon monoxide alarms. The relevant regulations required existing private rented properties to comply by 1 December 2024. |
Do Interlinked Smoke Alarms Need WiFi?
Interlinked smoke alarms don't need WiFi because they use radio frequency signals to communicate with each other directly. The alarms pair with one another during setup and continue to work as a closed local network, completely independent of your router or broadband connection.
This is an important distinction, because it means an interlinked alarm system keeps working even if your internet goes down or your WiFi router loses power. The alarms aren't relying on your network to trigger each other. They're communicating directly, alarm to alarm.
WiFi only comes into play if you want an extra layer on top of interlinking: smartphone notifications when an alarm is triggered, so you can be alerted even when you're not home. That's an optional add-on, not a requirement for interlinking to function. If you want that feature, a WiFi Gateway or SMART range system connects your interlinked alarms to an app, without changing how the core RF interlinking itself works.
Choosing an Interlinked Alarm System
Once you know you need an interlinked system, the main decision is how much control you want beyond the alarms themselves sounding together.
Our CORE range covers wireless interlinking with pre-set bundles prelinked and ready to install. CORE alarms come with a sealed, tamper-proof 10-year battery either as the main power source (Grade F1), or the backup in the mains-powered alarms (Grade D1), and require no maintenance beyond routine testing. We do recommend regularly wiping them with a dry cloth and removing dust with a vacuum or compressed air.
Our SMART range adds an optional WiFi Gateway on top of the same RF interlinking, so you get phone notifications and remote monitoring if an alarm is triggered while you're out. Both ranges are available in battery-powered (Grade F1) and mains-powered (Grade D1) options.
Each alarm type is tested and certified against the standards applicable to that type of alarm, rather than every alarm being certified to every standard. Smoke alarms, heat alarms and carbon monoxide alarms have their own relevant product standards and certification requirements.
Where LINKD Alarms fit
LINKD Alarms are designed to interlink as one system, whether they're mains or battery powered. Every alarm in our range can be wirelessly interlinked using radio frequency, and mains units can also be wired where that suits the installation.
Our interlinked alarms page covers our full range and the applicable certification for each alarm type.
Build your bundle of CORE or SMART interlinked alarms on our website. This lets you choose the exact mix of smoke, heat and carbon monoxide alarms for your property, and we can Pre-Link mixed mains and battery systems before dispatch, so the interlink setup is done before the alarms even arrive.
Review our CORE and SMART ranges thoroughly as alarms from different ranges cannot be linked together.
Frequently Asked Questions
Do all my alarms need to be the same brand to interlink?
Interlinked alarms need to use a compatible wireless protocol to communicate, so they do usually need to be from the same compatible range or manufacturer. Sticking to one manufacturer's range, like building a system entirely from LINKD alarms, helps ensure every unit will pair and trigger correctly.
Can I add more alarms to an existing interlinked system later?
Yes, many wireless interlinked systems, including LINKD's, are designed to expand. You can add compatible smoke, heat, carbon monoxide or accessory units to an existing system as your property changes, such as after an extension, without necessarily replacing what's already installed.
Do interlinked alarms still work during a power cut?
Battery-powered interlinked alarms are unaffected by a power cut, since they don't rely on mains electricity. Mains-powered interlinked alarms have a sealed back-up battery so they can continue to operate, including their interlinking function, if the mains supply fails.
How do I install an interlinked alarm system?
Wireless battery-powered interlinked alarms are designed for straightforward, tool-light installation. Pre-Linked bundles arrive already paired, so installation is simply mounting each alarm in the correct location using the supplied adhesive pads or screws, then testing the system to confirm every alarm responds as expected.
If you opt for mains-powered systems, the electrical installation should be carried out by someone competent to undertake the work and in accordance with the applicable requirements.
