CarbonDioxideConcentrationMeasurement Cluster

Cluster ID: 0x040D  |  Endpoint: Typically on Endpoint 1+ (application endpoint)

CarbonDioxideConcentrationMeasurement reports the CO2 (carbon dioxide) concentration in the air and is a core Cluster for indoor air quality monitoring. This is a read-only Server Cluster — it has no commands. The device passively collects data, and the App simply reads or subscribes.

Feature Bitmap

Concentration Measurement Clusters declare their supported measurement capabilities via FeatureMap (0xFFFC). Features directly determine which attributes are available — you must read FeatureMap first to decide what data the UI should display.

Attribute Overview

All attributes are read-only and divided into four groups. The Feature column indicates which Feature is required for that attribute to exist. Click an attribute ID to jump to its detailed description.

Numeric Measurement (MEA Feature)

Peak and Average Measurement

Level Indication (LEV Feature)

Attributes

MeasuredValue (Current Concentration)

The most recent CO2 concentration reading from the sensor. This is the most important attribute of the entire Cluster. Unlike the Temperature Cluster, Concentration Clusters use a float type — the value is the actual concentration and requires no conversion.

• Type: float (single-precision floating point)
• Unit: Determined by the MeasurementUnit attribute (typically PPM)
• Nullable: null indicates invalid sensor data or that the first measurement has not yet completed
• Feature: MEA

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MinMeasuredValue (Minimum Measurable Concentration)

The lowest concentration the sensor can measure. The App can use this to set the lower bound of the display range. For CO2 sensors, this is typically 400 ppm (atmospheric background concentration).

• Type: float, Nullable
• Feature: MEA

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MaxMeasuredValue (Maximum Measurable Concentration)

The highest concentration the sensor can measure. When MeasuredValue approaches this upper limit, it may indicate the sensor is beyond its normal operating range. For CO2 sensors, common upper limits are 5000 or 10000 ppm.

• Type: float, Nullable
• Feature: MEA

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PeakMeasuredValue (Peak Concentration)

The highest concentration recorded by the sensor within the time window specified by PeakMeasuredValueWindow. Useful for tracking "the worst air quality concentration in the last 24 hours."

• Type: float, Nullable
• Feature: PEA (depends on MEA)

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PeakMeasuredValueWindow (Peak Measurement Window)

The time window for PeakMeasuredValue, in seconds. For example, 86400 means the peak is the maximum value over the past 24 hours. When the window expires, PeakMeasuredValue resets and starts tracking again.

• Type: elapsed-s (uint32, elapsed seconds)
• Feature: PEA

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AverageMeasuredValue (Average Concentration)

The arithmetic average of concentration within the time window specified by AverageMeasuredValueWindow. The average is more stable than real-time values and is suitable for trend analysis and air quality scoring.

• Type: float, Nullable
• Feature: AVG (depends on MEA)

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AverageMeasuredValueWindow (Average Measurement Window)

The time window for AverageMeasuredValue, in seconds. For example, 3600 means the average is calculated over the past 1 hour.

• Type: elapsed-s (uint32, elapsed seconds)
• Feature: AVG

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Uncertainty (Measurement Uncertainty)

The sensor's measurement precision, in the same unit as MeasurementUnit. For example, a value of 15.0 with the unit PPM means the measurement accuracy is ±15 ppm. When using concentration thresholds to trigger automation, uncertainty should be taken into account.

• Type: float
• Feature: MEA

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MeasurementUnit (Measurement Unit)

Declares the unit of measurement used by numeric attributes such as MeasuredValue. The vast majority of CO2 sensors use PPM (parts per million). See MeasurementUnitEnum below for detailed enum values.

• Type: enum8
• Feature: MEA

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MeasurementMedium (Measurement Medium)

Declares which medium the sensor measures concentration in. CO2 sensors almost always use Air, but the Concentration Measurement Cluster family also covers water quality monitoring (Water) and soil monitoring (Soil). See MeasurementMediumEnum below for detailed enum values.

• Type: enum8
• Feature: MEA

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LevelValue (Concentration Level)

The device's own assessment of the current concentration level. Suitable for scenarios that don't require precise values — such as a simple traffic-light indicator. Note: If the device does not have the MED Feature, LevelValue will not return Medium; without the CRI Feature, it will not return Critical. See LevelValueEnum below for detailed enum values.

• Type: enum8
• Feature: LEV

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Commands

CarbonDioxideConcentrationMeasurement is a read-only Server Cluster with no commands. The device is responsible for collecting CO2 concentration and updating attributes; the App only needs to Read or Subscribe to obtain data.

Enum Quick Reference

MeasurementUnitEnum (Measurement Unit)

MeasurementMediumEnum (Measurement Medium)

LevelValueEnum (Concentration Level)

Example Data

Reading all attributes from an indoor CO2 sensor (typical indoor environment, approximately 800 ppm):

{
  // --- CarbonDioxideConcentrationMeasurement Cluster (Endpoint 1) ---

  // Numeric Measurement (MEA Feature)
  "0x00": 823.5,          // MeasuredValue = 823.5 ppm (current CO2 concentration)
  "0x01": 400.0,          // MinMeasuredValue = 400 ppm (sensor lower limit)
  "0x02": 5000.0,         // MaxMeasuredValue = 5000 ppm (sensor upper limit)
  "0x07": 15.0,           // Uncertainty = ±15 ppm

  // Measurement Unit and Medium (MEA Feature)
  "0x08": 0,              // MeasurementUnit = PPM
  "0x09": 0,              // MeasurementMedium = Air

  // Peak Measurement (PEA Feature)
  "0x03": 1250.0,         // PeakMeasuredValue = 1250 ppm (historical peak)
  "0x04": 86400,          // PeakMeasuredValueWindow = 86400 seconds (24-hour window)

  // Average Measurement (AVG Feature)
  "0x05": 680.5,          // AverageMeasuredValue = 680.5 ppm (average)
  "0x06": 3600,           // AverageMeasuredValueWindow = 3600 seconds (1-hour window)

  // Level Indication (LEV Feature)
  "0x0A": 2               // LevelValue = Medium
}

Read request example — read all Cluster attributes at once:

{
  // Read all CO2 Cluster attributes at once
  "readRequests": [{
    "attributePath": {
      "endpointId": 1,
      "clusterId": "0x040D"
      // No attributeId specified → reads all attributes
    }
  }]
}

Subscribe to CO2 concentration changes — track air quality in real time:

{
  // Subscribe to CO2 concentration changes (reports every 30 seconds to 5 minutes)
  "subscribeRequests": [{
    "attributePath": {
      "endpointId": 1,
      "clusterId": "0x040D",
      "attributeId": "0x00"        // MeasuredValue
    },
    "minIntervalFloor": 30,
    "maxIntervalCeiling": 300
  }]
}

Common Scenarios