Direct comparison
Smoke and carbon monoxide are not interchangeable warnings
Smoke alarms respond to particles or effects associated with fire. Heat alarms respond to temperature conditions and can be useful where ordinary cooking fumes would cause unwanted smoke alarms. Carbon monoxide alarms respond to a toxic, colourless gas produced by incomplete combustion.
A combined product may contain more than one certified sensor, but a device marketed as a smoke alarm alone should not be assumed to detect CO. Read the exact product markings, standards and end-of-life information.
| Alarm type | Principal warning | Typical positioning decision |
|---|---|---|
| Smoke alarm | Products of fire | Escape routes, halls, landings and rooms as the property guidance requires |
| Heat alarm | Rapid rise or high temperature | Kitchens or other locations where smoke detection may be unsuitable |
| Carbon monoxide alarm | CO from combustion | In rooms with relevant fixed combustion appliances and other positions identified by guidance |
| Combined alarm | Two or more stated hazards | Only where every sensor and position suits the intended risks |
England rented homes
The 2015 Regulations as amended set minimum landlord duties
For specified private and social rented homes in England, landlords must ensure a smoke alarm is equipped on each storey where there is a room used wholly or partly as living accommodation.
A CO alarm is required in any room used wholly or partly as living accommodation that contains a fixed combustion appliance, excluding gas cookers. Landlords must test required alarms at the start of a new tenancy and repair or replace a reported faulty alarm as soon as reasonably practicable after establishing it is not working.
Selection and placement
Choose the sensor and position together
GOV.UK home guidance identifies ceiling positions, hallways and landings for smoke detection and warns against ordinary smoke alarms in or near kitchens and bathrooms where fumes or steam can cause nuisance activations. Follow each product’s exact clearances.
CO alarm positioning should follow the manufacturer and government guidance for the appliance and room. Do not mount either device where furniture, curtains, strong airflow, condensation or inaccessible height undermines detection or maintenance.
- Every relevant storey considered
- Smoke, heat and CO hazards identified separately
- Product standard and expiry information checked
- Alarm can be heard or otherwise received by occupants
- Interconnection considered for the layout
- Resident disability and sleeping risk considered
Ongoing protection
Testing confirms the warning circuit—not the absence of risk
Use the approved test control at the interval in the product and housing guidance. GOV.UK general home advice recommends testing smoke alarms at least monthly. Never use flame, smoke, vehicle exhaust or another hazardous source as a test method.
Replace the specified battery or complete sealed-life alarm when required. A tenant should report a fault promptly; the landlord’s amended regulatory duty to repair or replace does not remove the occupant’s interest in routine testing and immediate safety.