How to choose a smoke alarm
Almost every alarm on the market looks identical in a photograph and claims the same five things. The differences live in a specification sheet and in a certificate number — and they are what you are actually paying for.
The six questions that decide everything
- Where will it be installed?Circulation spaces and bedrooms take smoke sensing. Kitchens, garages and dusty rooms take heat sensing. Fuel-burning appliances and garages need CO detection as well. The room chooses the technology; you choose the brand.
- What power is available?No wiring and no appetite for an electrician means a sealed 10-year battery unit. New build, rewiring or a landlord's duty of care points at mains-powered units with a backup cell and a hardwired interlink.
- Must they all sound together?In any occupied building, yes. A standalone alarm in a closed spare room protects the spare room. Wireless interlinking solves this without chasing walls.
- Which standard applies?Match the standard to the market: EN 14604, UL 217, GB 20517, AS 3786. A certificate against the wrong standard is not a certificate for your purpose.
- How loud, and with what pattern?At least 85 dB(A) at three metres, ideally a modulated tone. If the building has hard-of-hearing occupants or a noisy environment, add visual alarm devices.
- Who will maintain it?Sealed units remove the annual battery change, which is the maintenance step most often skipped. Check that the test and silence buttons are reachable from the floor for the person who will actually use them.
Decoding a specification sheet
| Specification line | What to look for | Common trap |
|---|---|---|
| Standard / certification | Certificate number, standard including amendment year, issuing body | “Designed to meet EN 14604” — a design claim, not certification |
| Sensor | Optical, ionisation, dual, heat; chamber design and insect resistance | “Multi-criteria” with no detail on which criteria or how they are combined |
| Sound pressure | ≥ 85 dB(A) at 3 m, stated as measured, with a frequency description | A peak figure measured at 10 cm quoted as though it were the 3 m rating |
| Battery | Chemistry, rated life, whether replaceable, low-battery warning behaviour | A “10-year battery” that is replaceable — not the same as a sealed 10-year unit |
| Operating temperature / humidity | Actual rated range, e.g. 0–40 °C at 10–90 % RH | Ranges omitted because the unit is only suitable for climate-controlled rooms |
| Interlink | Hardwired or radio, maximum number of units, maximum link distance | Radio range quoted for open air, not through reinforced concrete |
| IP rating | Stated to IEC 60529 where relevant | “Suitable for damp areas” with no rating at all |
| Service life | Manufacturer's replacement interval, usually 10 years | No replacement date on the label, so nobody knows when it expires |
No certificate number. A price that is a third of the market rate for a certified product. Instructions that are not in the language of the market being sold into. No model-specific marking on the device itself. A “test” button that only lights an LED without sounding the sounder. Technical data that quotes sensitivity without any reference to a standard. Any of these means walk away — an uncertified life-safety device is worse than none, because it is trusted.
What you are really buying over ten years
| Option | Initial | Batteries over 10 years | Maintenance visits | Verdict |
|---|---|---|---|---|
| Replaceable 9 V alkaline, changed yearly | Lowest | 10 batteries | 10 changes | Cheapest on paper, highest chance of a dead alarm in year three |
| Replaceable lithium 9 V | Low | 1–2 cells | 1–2 changes | Reasonable for owner-occupied homes |
| Sealed 10-year lithium | Moderate | None | None | Lowest risk; replacement coincides with sensor end of life |
| Mains-powered with backup and interlink | Highest, plus wiring | One backup cell | Minimal | The right answer in new build, rewired property and managed housing |
A five-minute check when the box arrives
- The certificate number on the product matches the one on the paperwork you were shown.
- The model number on the device matches the certificate and the manual.
- The label has a place for the installation date and a clear replacement interval.
- The test button produces a full alarm sound, not merely a light.
- The instructions include your language and the mounting clearances this site describes.
- For a wireless unit: the pairing procedure is documented and the maximum number of linkable units is stated.
Number and placement matter more than the model
A mid-range certified alarm correctly placed in every circulation space and every bedroom protects a family far better than one premium device in a hallway. Buy enough devices to cover the building properly, then spend what is left on quality — in that order. The coverage calculator and the placement checker will do the arithmetic with you.
Comparing quotations from suppliers?
Send the specification and the certificate numbers and we will tell you plainly whether the products actually meet the standard they claim.