How many smoke and carbon monoxide alarms do you need in England, and where do you fit them?

In England, rented homes need smoke alarms by storey and carbon monoxide alarms by room, but the legal trigger is narrower than many landlord checklists suggest. The rules below are for England only.

What alarms does a rental property need overall?

A rental property in England legally needs smoke alarms and, where the room trigger is met, carbon monoxide alarms; English rental alarm regulations do not impose a heat-alarm duty. The core duty is that “a smoke alarm is equipped on each storey of the premises on which there is a room used wholly or partly as living accommodation” and “a carbon monoxide alarm is equipped in any room of the premises which is used wholly or partly as living accommodation and contains a [fixed combustion appliance other than a gas cooker]”. Heat detectors can be sensible in kitchens, but the government’s landlord booklet says, “Heat detectors are not a replacement for smoke alarms.” Abodient can hold the property’s compliance obligations, certificates and expiry dates by jurisdiction, which matters because England, Wales and Scotland do not ask for the same alarm set. Wales differs because smoke alarms must be mains-connected and interlinked; Scotland differs because its standard covers every home and requires satisfactory fire and carbon monoxide detection equipment.

How many smoke alarms does a rented property need?

A rented property in England needs one smoke alarm on each storey that has a room used wholly or partly as living accommodation, not one per bedroom, room or square metre. The legal wording is “a smoke alarm is equipped on each storey of the premises on which there is a room used wholly or partly as living accommodation”, and the same regulation says “a bathroom or lavatory is to be treated as a room used as living accommodation.” Government guidance restates this as “At least one smoke alarm should be installed on every storey which is used as living accommodation,” but the statutory counting unit is the storey. “Storey” is not specially defined: the government says, “‘Storey’ is not defined in the regulations. It should be given its ordinary meaning.” The market usually installs more than the legal minimum where layout or risk justifies it, because the legal count is a floor-counting rule, not a fire-design standard. Wales requires mains-wired interlinked smoke alarms; Scotland fixes a broader pattern including circulation spaces and a kitchen heat alarm.

Where do you fit a smoke alarm?

The “7.5m from every habitable room door” and “300mm from walls” figures are not current English rental-law or Approved Document B smoke-alarm siting rules; the rental regulations do not stipulate where smoke alarms must be placed. The government’s landlord guidance states plainly, “The regulations do not stipulate where the alarms should be placed.” It then gives the practical recommendation: “Landlords should follow the individual manufacturer's instructions when installing the alarms. However, in general, smoke alarms should be fixed to the ceiling in a circulation space, i.e. a hall or a landing.” Approved Document B does not add a 7.5m or 300mm siting rule for existing rented homes; its relevant line says, “Smoke alarms should be provided in the circulation spaces of the dwelling in accordance with paragraphs 1.1 to 1.4.” The 300mm point is a manufacturer and fire-service dead-air convention, not the English rental-law rule. Scotland differs because ceiling mounting is effectively mandatory, with wall mounting only as a narrow exception.

In which rooms is a carbon monoxide alarm legally required?

In England, a carbon monoxide alarm is legally required in each room used wholly or partly as living accommodation that contains a fixed combustion appliance, except a gas cooker, so the number is one per qualifying room rather than one per house. The regulation requires “a carbon monoxide alarm is equipped in any room of the premises which is used wholly or partly as living accommodation and contains a fixed combustion appliance other than a gas cooker.” A hallway can count, because the same regulation says “‘room’ includes a hall or landing,” and a bathroom or lavatory can count because “a bathroom or lavatory is to be treated as a room used as living accommodation.” A fixed combustion appliance is the trigger, not gas supply in general, so an all-electric rental normally has no CO-alarm duty under this rule. Wales is stricter because it includes rooms with gas appliances, oil-fired combustion appliances or solid fuel burning combustion appliances, so cookers count; Scotland is broader again because it covers rooms with a fixed combustion appliance or a flue.

Do you need a carbon monoxide alarm for a combi boiler or a gas fire?

Yes, in an English rented property you need a carbon monoxide alarm in the room containing a combi boiler, gas boiler or gas fire, because those are fixed combustion appliances; a gas cooker alone is the carve-out. Government guidance defines the appliance as “a fixed apparatus where fuel of any type is burned to generate heat” and gives examples including “gas or oil boilers, or log-burning stoves.” The key correction is timing: gas boilers only came into the English rental CO-alarm duty from 1 October 2022, because before the amendment the wording was limited to a “solid fuel burning combustion appliance.” Building Regulations guidance also says, “Where a new or replacement fixed gas burning appliance (excluding gas appliances used solely for cooking) is installed in a dwelling, a carbon monoxide alarm should be provided in the room where the appliance is located.” A purely decorative fireplace does not trigger the duty: government guidance says “a non-functioning purely decorative fireplace would not constitute a fixed combustion appliance.”

Where do you position a carbon monoxide alarm?

English rental law does not fix the exact position of a carbon monoxide alarm, but government guidance says to follow the manufacturer’s instructions and generally place it at head height, about 1 to 3 metres from the possible carbon monoxide source. The landlord booklet says, “The regulations do not stipulate where the alarms should be placed,” and then states, “Landlords should follow the individual manufacturer's instructions when installing the alarms. However, in general, carbon monoxide alarms should be positioned at head height, either on a wall or shelf, approximately 1-3 metres away from a potential source of carbon monoxide.” Building Regulations guidance gives more precise installation distances for relevant appliance work: “on the ceiling at least 300mm from any wall or, if it is located on a wall, as high up as possible (above any doors and windows) but not within 150mm of the ceiling; and between 1m and 3m horizontally from the appliance.” Do not hide a CO alarm in a cupboard or behind furniture; obstruction defeats the point.

Who is responsible for testing and maintaining smoke and carbon monoxide alarms - the landlord or the tenant?

No English law makes anyone test an alarm during a tenancy: the landlord’s legal duties are to check prescribed alarms on day one of a new tenancy and to repair or replace a prescribed alarm after a tenant reports it faulty. The regulation requires “checks are made by or on behalf of the landlord to ensure that each prescribed alarm is in proper working order on the day the tenancy begins if it is a new tenancy.” After move-in, the duty is reactive: where a tenant reports a prescribed alarm and it is found not to be working, “the alarm is repaired or replaced.” Monthly testing is guidance, not a legal duty: How to Rent says, “Regularly test your smoke alarms and carbon monoxide detectors – at least once a month.” The practical problem is that this guidance is widely ignored; in 2024-25, 29% of private renters reported that they had never tested their smoke alarm. The £5,000 penalty attaches to ignoring a remedial notice, not simply to a missing alarm. Wales differs because the landlord’s working-order duty continues throughout occupation.

Since when have smoke and carbon monoxide alarms been a legal requirement?

In England, smoke alarms and solid-fuel carbon monoxide alarms became a private-rented-sector legal requirement on 1 October 2015, and CO alarms for gas boilers and similar fixed combustion appliances were added on 1 October 2022. The 2015 regulations say they “come into force on 1st October 2015,” while the Smoke and Carbon Monoxide Alarm (Amendment) Regulations 2022 say they “come into force on 1st October 2022.” That 2022 date matters because many summaries imply all CO duties began in 2015, but gas boilers were not brought into the rental duty until seven years later. The older Smoke Detectors Act 1991 is a historical trap: Parliament passed it, but the government later said the Act was unnecessary and “decided… not to bring that Act into force.” Compliance has not become universal simply because the rule is old; in 2024, only 52% of private rented sector dwellings with a solid fuel appliance had a carbon monoxide alarm. Wales began its current occupation-contract regime on 1 December 2022; Scotland’s current tolerable-standard alarm extension took effect on 1 February 2022 and binds every home.

What should a tenant do if the carbon monoxide alarm goes off?

If a tenant’s carbon monoxide alarm goes off in England, the safest instruction is to leave the property, ventilate if they can do so without delay or risk, call the National Gas Emergency Service on 0800 111 999, seek medical advice, and not re-enter until advised. There is no statute telling an occupier what they must do when a CO alarm sounds, but Gas Safe Register’s alarm-specific advice says, “if the alarm is sounding continuously this could be due to carbon monoxide being present in the air” and tells occupants to “turn off your gas supply, open windows and doors, leave the property and contact your nations gas emergency helpline.” NHS advice is stricter about re-entry: “get medical advice as soon as possible – do not go back into the affected building until you have got advice.” HSE’s domestic CO page includes the emergency number — “Call the National Gas Emergency Service on 0800 111 999” — but does not expressly tell the occupier to leave. For a landlord answering a 1am message, treat the sounding alarm as real until proved otherwise, not as a nuisance reset.

Last reviewed January 2026.

Sources

• “A rental property in England legally needs smoke alarms and, where the room trigger is met, carbon monoxide alarms; English rental alarm regulations do not impose a heat-alarm duty." — — "a smoke alarm is equipped on each storey of the premises on which there is a room used wholly or partly as living accommodation; (ii) a carbon monoxide alarm is equipped in any room of the premises which is used wholly or partly as living accommodation and contains a [fixed combustion appliance other than a gas cooker]” Source
• “Heat detectors can be sensible in kitchens, but the government’s landlord booklet says, “Heat detectors are not a replacement for smoke alarms.”" — — "Heat detectors are not a replacement for smoke alarms.” Source
• “Wales differs because smoke alarms must be mains-connected and interlinked" — — "on each storey of the dwelling there is a smoke alarm which is— (a) in repair and proper working order, (b) connected to the dwelling's electrical supply, and (c) linked to every other smoke alarm in the dwelling which is connected to the electrical supply.” Source
• “Scotland differs because its standard covers every home and requires satisfactory fire and carbon monoxide detection equipment." — — "(j) has satisfactory equipment installed for detecting, and for giving warning of, fire or suspected fire; (k) has satisfactory equipment installed for detecting, and for giving warning of, carbon monoxide present in a concentration that is hazardous to health” Source
• “A rented property in England needs one smoke alarm on each storey that has a room used wholly or partly as living accommodation, not one per bedroom, room or square metre." — — "a smoke alarm is equipped on each storey of the premises on which there is a room used wholly or partly as living accommodation” Source
• “The same regulation says “a bathroom or lavatory is to be treated as a room used as living accommodation.”" — — "For the purposes of paragraph (1)(a), a bathroom or lavatory is to be treated as a room used as living accommodation.” Source
• “Government guidance restates this as “At least one smoke alarm should be installed on every storey which is used as living accommodation”" — — "At least one smoke alarm should be installed on every storey which is used as living accommodation.” Source
• “Storey” is not specially defined: the government says, “‘Storey’ is not defined in the regulations. It should be given its ordinary meaning.”" — — "'Storey' is not defined in the regulations. It should be given its ordinary meaning. In the department's view, for the purpose of these regulations, a mezzanine floor would not be considered a storey.” Source
• “Scotland fixes a broader pattern including circulation spaces and a kitchen heat alarm." — — "one smoke alarm in every circulation space on each storey, such as hallways and landings” Source
• “The rental regulations do not stipulate where smoke alarms must be placed." — — "The regulations do not stipulate where the alarms should be placed.” Source
• “It then gives the practical recommendation: “Landlords should follow the individual manufacturer's instructions when installing the alarms. However, in general, smoke alarms should be fixed to the ceiling in a circulation space, i.e. a hall or a landing.”" — — "Landlords should follow the individual manufacturer's instructions when installing the alarms. However, in general, smoke alarms should be fixed to the ceiling in a circulation space, i.e. a hall or a landing.” Source
• “Approved Document B does not add a 7.5m or 300mm siting rule for existing rented homes; its relevant line says, “Smoke alarms should be provided in the circulation spaces of the dwelling in accordance with paragraphs 1.1 to 1.4.”" — — "1.9 Smoke alarms should be provided in the circulation spaces of the dwelling in accordance with paragraphs 1.1 to 1.4.” Source
• “The 300mm point is a manufacturer and fire-service dead-air convention, not the English rental-law rule." — — "Site alarms 300mm from walls, light fittings or any obstructions – this is to ensure that they are outside of any 'dead air' spaces that occur in corners and spaces where the airflow may be blocked.” Source
• “Scotland differs because ceiling mounting is effectively mandatory, with wall mounting only as a narrow exception." — — "Alarms on walls should be located within 30 cm of the ceiling at its highest end.” Source
• “In England, a carbon monoxide alarm is legally required in each room used wholly or partly as living accommodation that contains a fixed combustion appliance, except a gas cooker, so the number is one per qualifying room rather than one per house." — — "a carbon monoxide alarm is equipped in any room of the premises which is used wholly or partly as living accommodation and contains a fixed combustion appliance other than a gas cooker” Source
• “A hallway can count, because the same regulation says “‘room’ includes a hall or landing,”" — — "'room' includes a hall or landing” Source
• “A bathroom or lavatory can count because “a bathroom or lavatory is to be treated as a room used as living accommodation.”" — — "a bathroom or lavatory is to be treated as a room used as living accommodation” Source
• “Wales is stricter because it includes rooms with gas appliances, oil-fired combustion appliances or solid fuel burning combustion appliances, so cookers count" — — "The landlord must ensure that, during each period of occupation, a carbon monoxide alarm which is in repair and proper working order is in each room of the dwelling which contains a gas appliance, an oil-fired combustion appliance or a solid fuel burning combustion appliance.” Source
• “Scotland is broader again because it covers rooms with a fixed combustion appliance or a flue." — — "CO detectors to be fitted in all rooms where there is a fixed combustion appliance (excluding an appliance used solely for cooking) or a flue.” Source
• “Yes, in an English rented property you need a carbon monoxide alarm in the room containing a combi boiler, gas boiler or gas fire, because those are fixed combustion appliances; a gas cooker alone is the carve-out." — — "This means a fixed apparatus where fuel of any type is burned to generate heat. Typically, these appliances are powered by gas, oil, coal, wood, etc., for example, gas or oil boilers, or log-burning stoves.” Source
• “Gas boilers only came into the English rental CO-alarm duty from 1 October 2022, because before the amendment the wording was limited to a “solid fuel burning combustion appliance.”" — — "solid fuel burning combustion appliance” Source
• “Building Regulations guidance also says, “Where a new or replacement fixed gas burning appliance (excluding gas appliances used solely for cooking) is installed in a dwelling, a carbon monoxide alarm should be provided in the room where the appliance is located.”" — — "Where a new or replacement fixed gas burning appliance (excluding gas appliances used solely for cooking) is installed in a dwelling, a carbon monoxide alarm should be provided in the room where the appliance is located.” Source
• “A purely decorative fireplace does not trigger the duty: government guidance says “a non-functioning purely decorative fireplace would not constitute a fixed combustion appliance.”" — — "In the department's view, a non-functioning purely decorative fireplace would not constitute a fixed combustion appliance.” Source
• “English rental law does not fix the exact position of a carbon monoxide alarm" — — "The regulations do not stipulate where the alarms should be placed.” Source
• “Government guidance says to follow the manufacturer’s instructions and generally place it at head height, about 1 to 3 metres from the possible carbon monoxide source." — — "Landlords should follow the individual manufacturer's instructions when installing the alarms. However, in general, carbon monoxide alarms should be positioned at head height, either on a wall or shelf, approximately 1-3 metres away from a potential source of carbon monoxide.” Source
• “Building Regulations guidance gives more precise installation distances for relevant appliance work" — — "on the ceiling at least 300mm from any wall or, if it is located on a wall, as high up as possible (above any doors and windows) but not within 150mm of the ceiling; and between 1m and 3m horizontally from the appliance.” Source
• “Do not hide a CO alarm in a cupboard or behind furniture; obstruction defeats the point." — — "in an enclosed space (for example in a cupboard or behind a curtain) where it can be obstructed (for example by furniture) directly above a sink next to a door or window next to an extractor fan” Source
• “The landlord’s legal duties are to check prescribed alarms on day one of a new tenancy and to repair or replace a prescribed alarm after a tenant reports it faulty." — — "checks are made by or on behalf of the landlord to ensure that each prescribed alarm is in proper working order on the day the tenancy begins if it is a new tenancy” Source
• “After move-in, the duty is reactive: where a tenant reports a prescribed alarm and it is found not to be working, “the alarm is repaired or replaced.”" — — "where, following a report made on or after 1st October 2022 by a tenant or by their nominated representative to the landlord, a prescribed alarm is found not to be in proper working order, the alarm is repaired or replaced.” Source
• “Monthly testing is guidance, not a legal duty: How to Rent says, “Regularly test your smoke alarms and carbon monoxide detectors – at least once a month.”" — — "Regularly test your smoke alarms and carbon monoxide detectors – at least once a month.” Source
• “In 2024-25, 29% of private renters reported that they had never tested their smoke alarm." — — "In 2024-25, 29% of private renters, 29% of social renters and 22% of owner occupiers reported they had never tested their smoke alarm.” Source
• “The £5,000 penalty attaches to ignoring a remedial notice, not simply to a missing alarm." — — "The enforcing authority can impose a civil penalty of up to £5,000 on landlords who do not comply with the remedial notice.” Source
• “Wales differs because the landlord’s working-order duty continues throughout occupation." — — "The landlord must ensure that, during each period of occupation, a carbon monoxide alarm which is in repair and proper working order is in each room of the dwelling which contains a gas appliance, an oil-fired combustion appliance or a solid fuel burning combustion appliance.” Source
• “In England, smoke alarms and solid-fuel carbon monoxide alarms became a private-rented-sector legal requirement on 1 October 2015" — — "These Regulations may be cited as the Smoke and Carbon Monoxide Alarm (England) Regulations 2015 and come into force on 1st October 2015.” Source
• “CO alarms for gas boilers and similar fixed combustion appliances were added on 1 October 2022." — — "These Regulations may be cited as the Smoke and Carbon Monoxide Alarm (Amendment) Regulations 2022 and come into force on 1st October 2022.” Source
• “The older Smoke Detectors Act 1991 is a historical trap: Parliament passed it, but the government later said the Act was unnecessary and “decided… not to bring that Act into force.”" — — "As a result of this change, the provisions of the Smoke Detectors Act 1991 are unnecessary, and we have therefore decided, on the advice of the Building Regulations Advisory Committee, not to bring that Act into force.” Source
• “In 2024, only 52% of private rented sector dwellings with a solid fuel appliance had a carbon monoxide alarm." — — "In 2024, 52% of private rented sector dwellings with a solid fuel appliance had a carbon monoxide alarm, this was lower than in 2023 (65%).” Source
• “Wales began its current occupation-contract regime on 1 December 2022" — — "1 December 2022 is the appointed day for the coming into force of the Act in so far as it is not already in force.” Source
• “Scotland’s current tolerable-standard alarm extension took effect on 1 February 2022 and binds every home." — — "S. 86(1)(j) (k) inserted (1.2.2022) by The Housing (Scotland) Act 1987 (Tolerable Standard) (Extension of Criteria) Order 2019 (S.S.I. 2019/8), arts. 1, 2” Source
• “Gas Safe Register’s alarm-specific advice says, “if the alarm is sounding continuously this could be due to carbon monoxide being present in the air” and tells occupants to “turn off your gas supply, open windows and doors, leave the property and contact your nations gas emergency helpline.”" — — "Please note that if the alarm is sounding continuously this could be due to carbon monoxide being present in the air. Please ensure you turn off your gas supply, open windows and doors, leave the property and contact your nations gas emergency helpline.” Source
• “NHS advice is stricter about re-entry: “get medical advice as soon as possible – do not go back into the affected building until you have got advice.”" — — "get medical advice as soon as possible – do not go back into the affected building until you have got advice” Source
• “HSE’s domestic CO page includes the emergency number — “Call the National Gas Emergency Service on 0800 111 999”" — — "Call the National Gas Emergency Service on 0800 111 999” Source
• “Call the National Gas Emergency Service on 0800 111 999" — — "England, Wales and Scotland 0800 111 999” Source