Where to put a carbon monoxide alarm in a flat or terrace

The basic rule

Gas Safe Register says it is advisable to fit a carbon monoxide alarm in every room with a gas appliance, following the manufacturer’s fitting instructions. For rented homes in England, the GOV.UK guidance on the 2022 regulations adds a general position: at head height, on a wall or shelf, about 1 to 3 metres from a potential source of carbon monoxide.

That gives you a starting point. The maker’s instructions for your particular alarm come first if they say something different.

Room by room

Room	Gas appliance often found	Alarm?	Notes
Kitchen	Combi boiler in a wall cupboard	Yes	Head height, 1 to 3 metres from the boiler, away from steam
Kitchen	Gas cooker only	Advisable, not required in rentals	Rented home rules exclude gas cookers
Living room	Gas fire	Yes	Not directly above the fire
Bathroom	Older boiler or water heater	Yes	GOV.UK says a bathroom counts as living accommodation
Bedroom	Gas fire or boiler	Yes	HSE has rules on gas appliances in bedrooms too
Hall or landing	Boiler in a cupboard off the hall	Yes, in the hall	Not inside a closed cupboard unless the maker allows it
Bedroom without an appliance	None	Worth considering	Gives a warning where people sleep
Loft room	Boiler moved into the loft	Yes	Also in the room below if people sleep near the flue route

Gas Safe recommends audible alarms marked to BS EN 50291-1:2010 for homes. It does not recommend “black spot” cards, because they make no sound.

Walthamstow’s Warner flats

Walthamstow has a housing type you will not find in most of London. The Warner Estate “half houses” are terraced houses split into two flats, each with its own front door and garden (Waltham Forest conservation appraisal). Two flats in one small house means two gas supplies and, usually, two boilers.

That affects where alarms go:

• The upstairs flat’s boiler may be in a kitchen or bathroom directly above a bedroom in the flat below.
• Flues from the two boilers may terminate close together on the rear wall.
• Each flat needs its own alarms. One flat’s alarm will not wake the neighbours.

If you live downstairs and the boiler above you is near your bedroom, an alarm in your bedroom is a sensible extra, even if your own flat has no gas appliance in that room.

The same thinking applies to Victorian terraces split into flats in Leyton and Leytonstone, and to the 1930s Warner homes around Highams Park.

Places to avoid

Your alarm’s instructions come first, but these spots commonly give poor readings or false alarms:

• Directly above a cooker, hob or sink
• Next to an extractor fan, open window or air vent, where fresh air dilutes the reading
• In a steamy bathroom right by the shower
• Behind curtains or furniture
• In a closed cupboard, unless the instructions say that is allowed
• Very close to the appliance, closer than the 1 metre general guide

If you are unsure, a Gas Safe registered engineer can advise when they service the boiler.

Boilers in cupboards and lofts

Many London flats have the boiler boxed into a kitchen cupboard or a hall cupboard. The alarm normally goes in the room the cupboard opens into, at head height and within the 1 to 3 metre range. In converted lofts in E17 and E10, boilers are sometimes moved into the loft. Put the alarm in the loft room, and think about the room below as well.

Concealed flues need a mention here. In some flats the boiler flue runs through a ceiling void before it reaches the outside wall. HSE says these flues need inspection hatches so an engineer can check them. A CO alarm does not replace that check, but it does give warning if a hidden flue joint fails.

Landlords in Waltham Forest

At the 2021 Census, 27.8% of Waltham Forest households rented privately (ONS). Waltham Forest runs a selective licensing scheme from May 2025 to April 2030 in most wards.

Under the England regulations, landlords must fit a CO alarm in every room used as living accommodation with a fixed combustion appliance, excluding gas cookers. They must check alarms work on the day a new tenancy begins and repair or replace faulty alarms once told about them. Our guide to carbon monoxide alarm rules for London landlords covers the detail.

Test it and date it

• Press the test button monthly, or as the instructions say.
• Write the replacement date on the alarm. Gas Safe says most last five to ten years.
• Replace any alarm that chirps with a fault or end of life warning.

If the alarm ever gives a loud continuous sound, do not wait to see if it stops. Open doors and windows, turn off the boiler or fire if you can, get everyone outside into fresh air and call 0800 111 999. If anyone feels very unwell, call 999.

London Gas Engineers can supply and fit CO alarms when we service or safety check your appliances. See our carbon monoxide alarms page.