CarbonMonoxideConcentrationMeasurement Cluster

Cluster ID: 0x040C  |  Endpoint: Typically on Endpoint 1 (application endpoint)

This Cluster reports the concentration of carbon monoxide (CO) in the air and belongs to the Matter Concentration Measurement family. It shares the same attribute structure, Feature bitmap, and enum definitions with other concentration measurement Clusters such as CO₂ and PM2.5 — only the measurement target and safety thresholds differ.

Feature Bitmap

Concentration measurement Clusters share the same set of Feature definitions. Devices declare their supported capabilities via FeatureMap (0xFFFC). Features determine which attributes are available — always check before reading.

Attribute Overview

All attributes are read-only. The App retrieves data via Read / Subscribe.

Key Enums

The following enums are shared across all concentration measurement Clusters. Only the two most commonly used in CO scenarios are listed here.

LevelValueEnum (Concentration Level)

MeasurementUnitEnum (Measurement Unit)

CO Safety Threshold Reference

The following thresholds are derived from WHO and UL 2034 standards, provided as a reference for App alarm strategy design. The actual LevelValue classification on a device is set by the manufacturer and may not align exactly with this table.

Integration with SmokeCOAlarm

In real products, CO sensor devices typically implement two Clusters simultaneously:

• SmokeCOAlarm (0x005C) — handles local audible/visual alarms and device interlock, providing boolean-style states such as COState (Normal / Warning / Critical)
• CarbonMonoxideConcentrationMeasurement (0x040C) — provides precise ppm values, supporting trend analysis and remote monitoring

The division of responsibility: SmokeCOAlarm determines "whether to alarm," while this Cluster reports "the exact ppm reading." App alarm logic should primarily follow SmokeCOAlarm's state, with this Cluster's values displayed as supplementary information.

Example Data

Reading all attributes from a CO sensor device (FeatureMap = MEA + LEV + AVG):

{
  // --- Concentration Measurements ---
  "0x0000": 3.2,          // MeasuredValue = 3.2 ppm (current CO concentration)
  "0x0001": 0.0,          // MinMeasuredValue = 0 ppm
  "0x0002": 1000.0,       // MaxMeasuredValue = 1000 ppm (sensor full-scale range)
  "0x0003": null,         // PeakMeasuredValue = null (PEA Feature not enabled)
  "0x0004": null,         // PeakMeasuredValueWindow (not enabled)
  "0x0005": 2.8,          // AverageMeasuredValue = 2.8 ppm
  "0x0006": 3600,         // AverageMeasuredValueWindow = 3600 seconds (1-hour average)

  // --- Uncertainty ---
  "0x0007": 1.5,          // Uncertainty = ±1.5 ppm

  // --- Unit and Medium ---
  "0x0008": 0,            // MeasurementUnit = PPM
  "0x0009": 0,            // MeasurementMedium = Air

  // --- Level Indication ---
  "0x000A": 0             // LevelValue = Low (Normal)
}

Subscribing to CO concentration and level changes (recommended min interval 10 seconds, max interval 60 seconds):

{
  "subscribeRequests": [{
    "attributePath": {
      "endpointId": 1,
      "clusterId": "0x040C",
      "attributeId": "0x0000"     // MeasuredValue
    },
    "minInterval": 10,
    "maxInterval": 60
  }, {
    "attributePath": {
      "endpointId": 1,
      "clusterId": "0x040C",
      "attributeId": "0x000A"     // LevelValue
    },
    "minInterval": 10,
    "maxInterval": 60
  }]
}

Usage Scenarios

Scenario 1: Garage Ventilation Interlock

Scenario 2: Kitchen Gas Safety

Developer Tips