Smoke alarm & CO alarm installation — London
Smoke alarm and carbon monoxide alarm installation across London
Compliant with the Smoke and Carbon Monoxide Alarm (Amendment) Regulations 2022. Grade D interlinked systems for HMOs and multi-storey rentals. CO alarms for every combustion appliance. All 33 London boroughs covered. Documentation suitable for council licensing audits and tenancy start checks.
The legal framework
What the 2022 Regulations require of London landlords
The Smoke and Carbon Monoxide Alarm (Amendment) Regulations 2022 came into force on 1 October 2022, updating the original 2015 Regulations and significantly extending the obligations placed on private sector landlords in England. The changes were driven by data showing that carbon monoxide poisoning from gas appliances — not just solid fuel burners — was responsible for a substantial proportion of CO-related deaths in rented properties each year.
Under the 2022 Regulations, private landlords in England must ensure at least one smoke alarm is installed on every storey of the property that is used as living accommodation. A storey containing only a bathroom or utility room still counts if it is used as part of the living accommodation — a common configuration in London maisonettes and split-level flats. The alarms must be in working order at the start of each new tenancy.
The most significant change from the 2015 Regulations is the extension of the CO alarm requirement to cover all fixed combustion appliances — not only solid fuel appliances as previously required. From 1 October 2022, a carbon monoxide alarm must be installed in every room of a rented property that contains a fixed combustion appliance including gas boilers, gas fires, oil-fired boilers, and log burners. Cookers are excluded from the definition of fixed combustion appliance for the purposes of the CO alarm requirement.
Landlords must repair or replace any alarm that is not working within a reasonable time of being notified by the tenant. Local authorities in London have the power to serve remedial notices on landlords who fail to comply, and can arrange for alarms to be installed at the landlord's expense if the notice is not complied with within 28 days. Civil penalties of up to £5,000 can be imposed for breaches.
Key changes from 2015 to 2022
What changed — and why it matters for your London portfolio
The 2015 Regulations required smoke alarms on every storey where there was a room used as living accommodation and a CO alarm only in rooms with a solid fuel combustion appliance — a wood-burning stove, open fire, or coal burner. The CO alarm requirement did not apply to gas boilers or gas fires under the 2015 framework.
The 2022 amendment closed that gap. Any London rental property with a gas boiler, gas fire, or oil-fired appliance now requires a CO alarm in the room where that appliance is located. For a typical London terraced house with a combi boiler in the kitchen and a gas fire in the reception room, that means two CO alarms: one in the kitchen and one in the reception room.
The 2022 Regulations also clarified the repair obligation, previously implicit, by explicitly requiring landlords to act within a reasonable time of notification. Previous to this clarification, the enforcement position of some London boroughs had been that the obligation was limited to the start of tenancy only. That ambiguity has been resolved.
- Smoke alarm required on every storey used as living accommodation
- CO alarm required in every room with any fixed combustion appliance
- Applies to gas boilers and gas fires (not just solid fuel — change from 2015)
- Alarm must be in working order at start of each tenancy
- Landlord must repair or replace within a reasonable time of notification
- Local authority enforcement powers and civil penalty up to £5,000
London HMO licence conditions
HMO alarm requirements go beyond the 2022 Regulations
While the 2022 Regulations set the minimum baseline for all private rented properties in England, Houses in Multiple Occupation (HMOs) in London are subject to additional fire safety requirements imposed through HMO licence conditions. London's 33 local authority licensing authorities each publish their own standard conditions, but the requirements are broadly consistent in specifying that HMOs must have an interlinked Grade D fire alarm system throughout — not simply standalone battery alarms in key locations.
An interlinked system means that when any single alarm in the property detects smoke or heat, every alarm in the property sounds simultaneously. This is critical in HMOs where occupants sleep in rooms separated from common areas by multiple closed fire doors: a smouldering fire beginning in a first-floor bedroom at 3am must be capable of waking an occupant sleeping in the basement. Without interlinking, the alarm in the basement gives no signal until the fire has spread to a storey where a separate detector is installed.
London HMO licence conditions typically require: Grade D (mains-powered with battery backup) alarms throughout, smoke alarms in every habitable room and circulation space, heat detectors in the kitchen, a CO alarm in every room with a combustion appliance, regular testing by the licence holder, and a written fire alarm test log maintained on the premises.
Interlinked Grade D alarms are now required not only in properties that hold an HMO licence but in all new residential buildings under Approved Document B of the Building Regulations. The 2019 amendment to Approved Document B extended the interlinking requirement to all new dwellings in England, reflecting the consensus in BS 5839 Part 6 that interlinking provides a substantially higher level of protection without the cost and complexity of a Grade A panel system.
For London landlords managing existing stock, fitting interlinked Grade D alarms is strongly recommended as best practice even where the licence conditions do not yet explicitly require it. The investment is modest — a three-bedroom HMO can be fully equipped with an interlinked Grade D system for £300–£600 including installation — and the protection it provides is meaningfully better than standalone battery alarms in hallways and landings only.
Detector types
Choosing the right alarm for each room in a London property
Not all smoke alarms detect the same type of fire. Matching detector technology to room function is a core part of BS 5839 Part 6 system design — and the difference between an alarm that wakes occupants in time and one that either sounds too late or triggers nuisance alarms that cause occupants to remove batteries.
Ionisation smoke alarm
Fast-flaming fires
- Detects small combustion particles from open, fast-burning fires
- Most effective for fires involving paper, wood, or volatile liquids
- Less effective at detecting slow, smouldering fires
- Prone to nuisance alarms from cooking — avoid kitchen placement
- Lower purchase cost than optical alarms
Optical (photoelectric) smoke alarm
RecommendedSmouldering fires — best for bedrooms
- Detects larger smoke particles from slow, smouldering fires
- Better suited to London's most common bedroom fire scenario
- Less susceptible to nuisance alarms from steam or cooking fumes
- Recommended by London Fire Brigade for living areas and bedrooms
- The preferred choice for LD2 and LD1 category installations
Heat detector
Kitchens — not a substitute for smoke alarms
- Activates on high temperature, not smoke particles
- Suitable for kitchens and garages where smoke alarms trigger falsely
- Significantly slower to respond than smoke alarms in living areas
- Does not satisfy the smoke alarm requirement under the 2022 Regulations
- Should be used in addition to smoke alarms, not instead of them
Combination (multi-sensor) alarm
Versatile — hallways and circulation spaces
- Combines optical and heat sensing in one unit
- Reduces both nuisance alarms and false negatives
- Suitable for open-plan kitchen-living areas
- Interlinks with Grade D systems using standard protocols
- Higher cost per unit but reduces need for separate device types
BS 5839 Part 6
British Standard categories explained: LD1, LD2, and LD3
BS 5839 Part 6 is the British Standard for the design, installation, commissioning, and maintenance of fire detection and alarm systems in domestic premises. It defines three life protection (LD) categories that determine the extent of coverage required.
LD3
Detectors only in escape routes — hallways and staircases. Provides warning when fire has spread to the circulation space. The lowest level of protection and generally insufficient for London rental properties with vulnerable occupants.
Typical use: Sole-occupancy owner-occupied properties only
LD2
Detectors in escape routes plus the principal rooms where fire is most likely to start — typically the kitchen, living room, and principal bedroom. Provides earlier warning than LD3 by detecting fire closer to its source before it spreads to the escape route.
Typical use: Most London private rented properties, basic HMOs
LD1
Detectors throughout all rooms, including storage areas, loft spaces, and utility rooms. The highest level of fire protection for a domestic system. Required under some HMO licence conditions and strongly recommended for large or high-risk properties.
Typical use: Large HMOs, high-value properties, vulnerable occupant properties
Alarm grades
Grade D vs Grade A: what does your London property need?
BS 5839 Part 6 defines alarm grades from A to F based on the power source and whether the system uses a central control panel. The two grades relevant to virtually all London residential properties are Grade D and Grade A.
Grade D
Standard for HMOsMains-powered, battery backup, self-contained
A Grade D alarm is a self-contained device combining the detector, sounder, and power supply in a single unit mounted on the ceiling. Mains-powered with an integral battery that maintains operation during a power cut, Grade D alarms can be interlinked via hardwired cable or radio frequency signal so that activation of any single alarm sounds all others on the property. No central panel is required. This makes Grade D the practical choice for all standard London rental properties, including most HMOs: the system is straightforward to install, does not require specialist maintenance contracts, and satisfies both the 2022 Regulations and the standard HMO licence conditions published by London boroughs.
Required for: New builds, HMOs, recommended for all London rental properties
Grade A
Large HMOs onlyFull fire alarm panel with separate detectors
A Grade A system consists of separate detection devices wired back to a central fire alarm control panel. The panel provides zone identification, fault monitoring, and event logging. It typically includes a remote monitoring connection to an alarm receiving centre (ARC) and may require quarterly maintenance visits by a fire alarm engineer under a maintenance contract. Grade A systems carry substantially higher installation and ongoing costs than Grade D systems and are only appropriate where the building scale or occupancy risk justifies the additional investment — typically registered HMOs with five or more storeys, or buildings where the fire risk assessment specifically requires a panel system.
Required for: Large HMOs (5+ storeys), commercial-standard buildings
Carbon monoxide alarm placement
Where to position CO alarms in a London rental property
Carbon monoxide is produced by the incomplete combustion of any fuel — gas, oil, solid fuel, or wood. It has a density very slightly lower than air, which means it distributes relatively uniformly throughout a room rather than accumulating at floor or ceiling level in the way that some heavier gases do. BS EN 50291, the European product standard for domestic CO alarms, and the manufacturer guidance based on it recommends placing CO alarms at head height — approximately 1.5 metres from the floor — rather than at ceiling height as with smoke alarms.
The alarm should be positioned at least one metre from the combustion appliance to avoid false alarms during the normal start-up and cool-down cycle of the appliance, and not directly above a cooker, hob, or other source of heat and steam that could affect sensor accuracy. In a kitchen where a boiler is located on the wall, a position on the opposite wall at head height, away from the cooker, is typically optimal.
For a log burner or open fire in a reception room, the CO alarm should be on the same floor and in the room with the appliance. For a boiler in a utility cupboard that opens into a kitchen, the alarm should be in the kitchen — not inside the closed cupboard — unless the cupboard is large enough to be used as a separate room.
The 2022 Regulations require a CO alarm in every room that contains a fixed combustion appliance. In a London terraced house with a combi boiler in the kitchen, a gas fire in the front reception room, and a wood-burning stove in the rear extension, three CO alarms are required — one in each room where a combustion appliance is located.
CO alarms should be replaced in accordance with the manufacturer's recommended service life, typically seven to ten years. Unlike smoke alarms, CO alarms have an electrochemical sensor that degrades over time regardless of use. A CO alarm beyond its service life may fail to respond to dangerous CO concentrations even if the test button continues to sound. Landlords should record installation dates and schedule replacements proactively as part of their planned maintenance programme.
- Position at head height (approximately 1.5m from floor)
- At least 1 metre from the combustion appliance
- Not directly above a cooker, hob, or steam source
- Required in every room with a fixed combustion appliance
- Replace per manufacturer guidance — typically 7–10 years
- Test at the start of each tenancy; record in maintenance log
The installation process
How we install smoke and CO alarms in London properties
Every installation follows a structured process designed to deliver a system that is both legally compliant and practically effective — not just a set of alarms fixed in legally required positions.
Compliance survey
We assess the property against the 2022 Regulations and the applicable BS 5839 Part 6 category for the tenancy type. HMO licence conditions are reviewed where relevant. A written installation schedule is produced showing detector locations and alarm grades.
Detector selection
Alarm type is matched to room function: optical alarms in bedrooms and hallways, heat detectors in kitchens, CO alarms in every room with a combustion appliance. Interlinked Grade D alarms are specified for HMOs and multi-storey properties.
Fixing and wiring
Mains-powered Grade D alarms are connected to a dedicated circuit or spur — not added to an existing lighting circuit in a way that disables them when a breaker trips. Battery-only alarms are fixed to ceiling positions per BS 5839 Part 6 placement guidance.
Interlinking verification
For interlinked systems, each detector is tested to confirm the interconnect trigger causes all alarms on the property to sound. Radio-linked systems are tested for signal integrity between floors and through walls, with repositioning where signal is marginal.
CO alarm placement
CO alarms are positioned at head height, at least 1 metre from the combustion appliance, and away from direct draughts. Carbon monoxide is slightly less dense than air and distributes throughout a room — head-height placement reflects both the gas behaviour and the position of an occupant sleeping or sitting.
Documentation
A completion record is issued showing detector locations, alarm grades, serial numbers, and test results. For HMO properties, a fire alarm log book is provided. Landlords receive documentation suitable for council licensing audits and tenancy start-of-period checks.
2025 pricing — London
Smoke and CO alarm installation costs in London
London alarm installation pricing reflects the type and grade of alarm, number of devices, and whether the system requires mains wiring or can be installed as a battery or radio-linked system. All prices include supply and installation of alarms, system testing, and a completion record for compliance documentation.
Single alarm — battery or mains
£60 – £120
Per alarm fitted. Includes supply of optical smoke alarm, heat detector, or CO alarm as required. Battery models at the lower end; mains-wired Grade D alarms towards the upper end. Minimum call-out applies for single-alarm visits.
Interlinked system — 3-bed HMO
£300 – £600
Full interlinked Grade D system for a typical three-bedroom London HMO: optical smoke alarms on each storey and in habitable rooms, heat detector in kitchen, CO alarm per combustion appliance. Hardwired or radio-linked depending on access.
Full LD1 system — large HMO
From £600
LD1 category coverage throughout including storage, utility, and ancillary spaces. Mains-wired Grade D interlinked system with fire alarm test log and documentation package suitable for HMO licence renewal submissions.
All prices include VAT. A firm fixed price is confirmed following a brief property assessment — alarm counts, appliance locations, and access for mains wiring are all factors that affect cost. Most residential jobs in London are assessed and quoted on the same visit as the installation.
Book today
Make your London rental property alarm-compliant
Gas Safe registered engineers covering all 33 London boroughs. Same-day and next-day appointments available. Compliance documentation issued on completion — suitable for council licensing audits and start-of-tenancy records.
Common questions
Smoke alarm and CO alarm installation London: frequently asked
Are battery smoke alarms legal in London rental properties?
Battery-only smoke alarms are technically permitted under the Smoke and Carbon Monoxide Alarm (Amendment) Regulations 2022 for properties that are not HMOs and do not fall under a mandatory licence condition requiring mains-powered alarms. However, most London borough HMO licences — covering any property let to three or more unrelated tenants — specify Grade D (mains-powered with battery backup) interlinked alarms as a licence condition. For a standard single-let property, a long-life sealed battery alarm such as the Aico Ei650RF meets the legal minimum. That said, mains-powered Grade D alarms are strongly recommended as best practice throughout London's private rental sector because they eliminate the common problem of tenants removing batteries. If a battery alarm is found to have a flat or missing battery at the time of a fire, the landlord may face enforcement action for failing to ensure the alarm was in working order.
Where should smoke alarms be positioned in a rental property?
BS 5839-6:2019 specifies that smoke alarms should be installed in circulation areas — hallways and landings — on every floor, and within 3 metres of every bedroom door. For a two-storey house this means at minimum one on the ground-floor hallway and one on the first-floor landing, both within 3 metres of bedroom doors. Additional alarms are required in all living rooms. Optical detectors are recommended for bedrooms and landings because they respond faster to slow-smouldering fires. Ionisation alarms are suited to kitchens and lounges where fast-flaming fires are more likely, though heat detectors rather than smoke alarms are generally preferred in kitchens to reduce false alarms from cooking. Alarms must not be positioned closer than 300mm to a wall-ceiling junction, within 300mm of a light fitting, or directly above a heater or air conditioning unit. CO alarms must be at head height — above 1.5m from the floor — and at least 1 metre from any combustion appliance.
Do I need a CO alarm with a combi boiler?
Yes. The Smoke and Carbon Monoxide Alarm (Amendment) Regulations 2022 came into force on 1 October 2022 and extended the requirement for CO alarms to every room containing a fixed combustion appliance. This is a significant change from the 2015 Regulations, which required CO alarms only in rooms with solid-fuel burning appliances. From October 2022, a CO alarm is legally required in every room where a gas boiler, gas fire, gas cooker, oil boiler, or wood-burning stove is installed. A combi boiler in a kitchen cupboard, a boiler in a bedroom, a gas fire in a living room — all require a CO alarm in that room. The alarm must conform to BS EN 50291 and must be in working order at the start of each tenancy. Note: open-flued gas appliances present the highest CO risk; condensing boilers flued externally present a lower but still real risk of CO ingress if the flue terminal is damaged or blocked.
What is Grade D vs Grade A for smoke alarms?
Grade D systems are mains-powered individual alarms with an integral battery backup, interconnected either by wiring or via radio-frequency (RF) wireless technology. When one alarm activates, all alarms in the network sound simultaneously — this is the interlinked requirement. Grade D is required by most London HMO licences, BS 5839-6 Category LD2 and LD3 designs, and is best practice across the London rental sector. The Aico 3000 Series and 7000 Series are widely specified because they use RF interconnect — no additional wiring is needed to link alarms across multiple floors. Grade A systems are panel-based systems with separate detection heads connected to a central control panel — the same type of system found in commercial buildings. Grade A is required in larger HMOs, typically those with four or more storeys or more than six occupants, and is specified in the more complex HMO licence conditions issued by London borough councils. Grade A installations require design by a competent person to BS 5839-1 and must be serviced and certificated annually.
Can tenants be held responsible for testing alarms?
Under the Smoke and Carbon Monoxide Alarm (Amendment) Regulations 2022, the landlord's legal duty is to ensure that all alarms are in working order at the start of each new tenancy. The Regulations do not require landlords to test alarms during a tenancy — the responsibility for ongoing testing during the tenancy sits with the tenant under the duty to not tamper with alarms. However, the landlord must repair or replace a faulty alarm within a reasonable time of being notified by the tenant. In practice, this means that a tenant who removes a battery, deliberately disables an alarm, or fails to notify the landlord of a fault can be held responsible for that specific breach. But the landlord cannot rely on tenant responsibility as a defence if they never tested the alarm at the start of the tenancy or did not keep a written record of that test. For HMOs, most licence conditions require a documented annual test by the landlord or managing agent regardless of tenant obligations — failure to produce the test log during an HMO inspection will trigger enforcement action.