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Zigbee devices Smoke and gas detectors

Develco HESZB-120

Fire detector with siren. Works with Zigbee2MQTT with no vendor hub or cloud: it pairs with a Zigbee stick and shows up in Home Assistant.

Vendor
Develco
Model
HESZB-120
Type
Smoke and gas detectors
Power
battery: an end device, does not extend the mesh
Firmware updates (OTA)
yes, through Zigbee2MQTT
Also sold as
Frient 94431

Find it in shops: AliExpress

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What it exposes

FeaturePropertyValuesControl
Reliabilityreliabilityno_fault_detected, unreliable_other, process_errorread only
Faultfault—read only
Temperaturetemperature°Cread only
Batterybattery% · 0…100read only
VoltagevoltagemVread only
Smokesmoke—read only
Low batterybattery_low—read only
Supervision reportssupervision_reports—read only
Restore reportsrestore_reports—read only
Testtest—read only
Warningwarning—read only
Max durationmax_durations · 0…600settable

MQTT: state and commands

Zigbee2MQTT publishes the device state to zigbee2mqtt/my_device (my_device is the name you give the device). An example message:

{
  "reliability": "no_fault_detected",
  "fault": false,
  "temperature": 21.6,
  "battery": 87,
  "voltage": 2950,
  "smoke": false,
  "battery_low": false,
  "supervision_reports": false,
  "restore_reports": false,
  "test": false,
  "max_duration": 300,
  "linkquality": 120
}

The device only reports data and takes no commands.

Watch the topics live from the browser: MQTT client.

Home Assistant automation example

Zigbee2MQTT creates Home Assistant entities from the device name. If it is called my_device, an automation in automations.yaml can look like this:

- alias: "Smoke alarm"
  mode: single
  triggers:
    - trigger: state
      entity_id: binary_sensor.my_device_smoke
      to: "on"
  actions:
    - action: notify.notify
      data:
        message: "Smoke detected!"

Check the YAML: YAML checker.

How to pair it

  1. In Zigbee2MQTT click Permit join.
  2. Put the device in pairing mode: usually a long press of the reset button (5–10 s) until the LED blinks; bulbs: switch the power off and on 5–6 times.
  3. Keep the device close to the coordinator or a router while pairing.
  4. Give it a clear name: MQTT topics and Home Assistant entities are built from it.

Exact procedure and model notes: the device page in the Zigbee2MQTT docs. No coordinator yet: coordinator picker.

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