frient
frient Intelligent Smoke Alarm (SMSZB-120)
- Zigbee
Verified September 2026
The Zigbee smoke alarm to buy in the UK: Danish-made (Develco), EN 14604 certified, and it works out of the box in Zigbee2MQTT — the 85dB siren doubles as an intruder sounder when triggered from Home Assistant. Unlike interlinked mains alarms, there's no native RF link between units; sounding several together needs a hub automation, not a built-in mesh. At Ø65x40mm on a magnetic ceiling bracket it's compact and tool-free to fit, but the CR123 battery and hub dependency are why it costs more than a basic £10 mains alarm. Treat it as a smart companion to, not a replacement for, your interlinked mains alarms.
In Home Assistant
| Control | Type | What it does |
|---|---|---|
| Smoke | Binary sensor | True when the optical chamber detects smoke; gate any HA-triggered siren automation on this being off so it never fires during a real fire event. |
| Alarm | Command (start/off) | Sounds or silences the 85dB siren on demand from HA; write-only, so there's no readback — track intended state in automation logic. |
| Max duration | Number (0-600s) | Siren cutoff, default 240s — caps how long an HA-triggered siren blast runs before auto-stopping. |
| Self-test | Binary sensor | Reflects self-test state, but only tests initiated through HA are visible here; pressing the physical self-test button does not surface as an HA event. |
| Temperature / battery | Sensor | Onboard temperature and battery percentage/voltage, reported alongside fault/reliability diagnostics for unit health monitoring. |
Zigbee2MQTT exposes smoke, battery, temperature and fault/reliability as read-only, plus a write-only alarm command (start/off) and a read/write max-duration setting (default 240s) that caps how long the siren runs once triggered from HA. The unit's physical self-test button doesn't surface as an HA event or log line — only the test property flips — so verification automations should poll that entity rather than assume a button press will fire anything. A subset of units fail to bind correctly during pairing and silently return null battery/temperature/fault values forever, so confirm those entities actually populate within a few minutes of joining. For a dual-purpose fire/intruder siren automation, gate any HA-triggered alarm start (e.g. door sensor while away) on the native smoke sensor being off first, and test the off command once after any firmware update — some Develco/frient firmware versions had a known bug where sending off re-triggered the siren instead of silencing it.
Specs
- power
- 1x CR123 replaceable battery, circa 3 years at default 5-minute reporting interval
- siren
- 85 dB at 3m, controllable as a Zigbee siren entity
- mounting
- Magnetic ceiling bracket, no drilling or screws required
- interlink
- No native RF interlink between units like mains-wired alarms — sounding multiple alarms together requires a Zigbee hub automation, not a standalone mesh
- dimensions
- Ø65 x 40mm, approx. 100g
- sensor type
- Optical (photoelectric) smoke sensor with onboard temperature sensor (0 to +50°C, ±0.5°C)
- certification
- EN 14604 (DIN); CE, RoHS, REACH compliant
- operating conditions
- IP20; 0 to +50°C, 10-95% RH non-condensing