frient
frient Intelligent Smoke Alarm (SMSZB-120)
- Zigbee2MQTT / ZHA
- Local control
- Zigbee
Prices verified September 2026
See more sensors picks on our Amazon storefront →Our verdict
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.
What can Home Assistant control on the frient Intelligent Smoke Alarm (SMSZB-120)?
| 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 |
How does the frient Intelligent Smoke Alarm (SMSZB-120) compare?
| Product | From | Protocol | Local control | Integration |
|---|---|---|---|---|
| frient Intelligent Smoke Alarm (SMSZB-120) (this product) | £55 | Zigbee | Yes | Zigbee2MQTT / ZHA |
| Aqara Door and Window Sensor P2 | £23.99 | Matter, Thread | Yes | Works with HA |
| Aqara Motion Sensor P1 | £18.99 | Zigbee | Yes | Zigbee2MQTT / ZHA |
| Aqara Multi-State Sensor P100 | £25.49 | Zigbee, Thread, Matter | Yes | Zigbee2MQTT / ZHA |
Frequently asked questions
- Does the frient Intelligent Smoke Alarm (SMSZB-120) work with Home Assistant locally?
- Yes. The frient Intelligent Smoke Alarm (SMSZB-120) is controlled locally in Home Assistant through Zigbee2MQTT or ZHA, so it keeps working if your internet connection or the frient cloud goes down. Control and state updates stay on your own network.
- Which protocol does the frient Intelligent Smoke Alarm (SMSZB-120) use, and do I need a hub?
- The frient Intelligent Smoke Alarm (SMSZB-120) uses Zigbee. To pair it with Home Assistant you need a Zigbee coordinator (for example a SkyConnect/ZBT-1 or Sonoff dongle) attached to your Home Assistant host. frient's own hub is not required when you integrate through Zigbee2MQTT or ZHA.
- How much does the frient Intelligent Smoke Alarm (SMSZB-120) cost in the UK?
- The lowest price we have listed for the frient Intelligent Smoke Alarm (SMSZB-120) is £55 at Amazon UK, with other UK retailers at up to £56.09. Prices were last checked in September 2026 and change often, so confirm on the retailer's page before buying.