SmokeCOAlarm Cluster

Cluster ID: 0x005C  |  Endpoint: Typically on Endpoint 1 (application endpoint)

SmokeCOAlarm is the core Cluster for fire safety devices in Matter, responsible for smoke detection, carbon monoxide (CO) detection, battery status monitoring, device self-testing, and interconnect alarms. Standalone smoke detectors, combination smoke/CO detectors, and interconnected alarm systems commonly found in residential settings all rely on this Cluster.

Feature Bitmap

SmokeCOAlarm declares its supported alarm capabilities via FeatureMap (0xFFFC):

Commands

The SmokeCOAlarm Cluster has only one command — trigger a device self-test. The core actions of an alarm device (alarming, muting, etc.) are triggered autonomously by the device and do not require external command control.

SelfTestRequest — Trigger Self-Test (0x00)

Requests the device to perform a self-test procedure. The device checks whether its sensors, buzzer, battery, and other components are functioning properly. During the self-test, the TestInProgress attribute becomes true, and the SelfTestComplete event is emitted upon completion. No parameters are required.

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Attributes

The SmokeCOAlarm Cluster attributes are organized into four groups. Click an attribute ID in the summary table below to jump to its detailed description.

Alarm State (0x0000 - 0x0003)

Describes the device's current alarm states. ExpressedState is the overall prioritized result of all states; the other three are individual states.

ExpressedState Enum Values

ExpressedState reflects the state that currently requires the most attention. Priority is listed from highest to lowest:

SmokeState / COState / BatteryAlert / InterconnectSmokeAlarm / InterconnectCOAlarm Enum Values

The five attributes above share the same three-level alarm enum:

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Device Control (0x0004 - 0x0007)

Describes the device's mute state, self-test progress, hardware health, and service lifetime.

DeviceMuted Enum Values

EndOfServiceAlert Enum Values

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Interconnect Alarm (0x0008 - 0x0009)

When multiple alarm devices are interconnected, if one device triggers an alarm, the others reflect that state through interconnect attributes. Interconnect alarms ensure the alarm can be heard throughout the entire home, even if the fire source is not in the same room as the current device.

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Sensor & Lifetime (0x000A - 0x000C)

Information related to sensor health and device service lifetime.

ContaminationState Enum Values

SmokeSensitivityLevel Enum Values

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Events

SmokeCOAlarm is one of the most event-rich Clusters in Matter. Events record the complete lifecycle of an alarm device from trigger to clearance, and are the primary data source for app push notifications and alarm history. All events have a priority of Critical.

Typical Event Sequence

A complete smoke alarm lifecycle produces the following event sequence:

1. SmokeAlarm — sensor detects smoke, alarm begins
2. AlarmMuted — user presses the mute button (optional)
3. MuteEnded — mute times out, alarm resumes (if smoke has not cleared)
4. AllClear — smoke dissipates, all alarm states return to normal

Example Data

A SmokeCOAlarm Cluster read result from a device supporting both smoke and CO alarms in a normal state:

{
  // --- Overall Alarm State ---
  "0x0000": 0,              // ExpressedState = Normal (no active alarms)
  "0x0001": 0,              // SmokeState = Normal
  "0x0002": 0,              // COState = Normal
  "0x0003": 0,              // BatteryAlert = Normal
  "0x0004": 0,              // DeviceMuted = NotMuted (not muted)
  "0x0005": false,          // TestInProgress = false (not self-testing)
  "0x0006": false,          // HardwareFaultAlert = false
  "0x0007": 0,              // EndOfServiceAlert = Normal

  // --- Interconnect Alarm ---
  "0x0008": 0,              // InterconnectSmokeAlarm = Normal
  "0x0009": 0,              // InterconnectCOAlarm = Normal

  // --- Sensor & Lifetime ---
  "0x000A": 0,              // ContaminationState = Normal
  "0x000B": 1,              // SmokeSensitivityLevel = Standard
  "0x000C": 1893456000      // ExpiryDate = 2029-12-31 (epoch_s)
}

Common Scenarios