ASTM D8624-25

1.1 This test method covers the usage of a chamber system equipped with a CO₂ reference monitor to evaluate the performance of stationary indoor air quality CO₂ sensors and CO₂ sensor systems used for CO₂ detection and measurement.

1.2 This test method evaluates, under steady state conditions (CO₂ concentrations, temperature, and relative humidity), indoor air quality CO₂ sensors and sensor systems on their capabilities to detect and measure CO₂ against a CO₂ reference monitor.

1.3 This test method is not intended to evaluate indoor air quality sensors and sensor systems for purposes of homeland security or other law enforcement or forensic activity.

1.4 This test method evaluates the performance of sensors and sensor systems that can continuously be powered and continuously operated in data collection mode for the duration of any test in this test method. Sensors and sensor systems must be powered either through line power or an internal battery of enough output to operate properly. Sensors and sensor systems without data storage and recording capabilities are not intended to be evaluated using this test method.

1.5 This test method evaluates sensors and sensor systems at standard atmospheric pressure. Atmospheric pressure can affect the performance of sensors or sensor systems in detecting and measuring CO₂. This test method is not intended to provide an evaluation specific to the atmospheric pressure conditions at the manufacturing site or end use location of the sensor or sensing systems. For guidance related to evaluating atmospheric pressure as an interferent to test sensors or test sensor systems, see Appendix X1.

1.6 The values stated in SI units are to be regarded as standard. Other units present in this standard are for information only. The non-SI unit of parts per million (ppm), as defined in 3.2.11, is also used.

1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

5.1 Poor indoor air quality has been implicated in significant adverse acute and chronic impacts on occupant health and performance. The ability to assess the various factors contributing to poor indoor air quality is critical for improving indoor air quality.

5.2 Indoor CO₂ concentrations have long been used as indicators of occupant-related indoor air quality issues, though many such applications of CO₂ reflect misunderstandings of the relationship between CO₂ and indoor air quality, and misinterpretations of measurement results. These CO₂ concentrations are determined primarily by the rate at which occupants generate CO₂ and dilution of CO₂ by ventilation. The impact of CO₂ on occupant health, comfort, and performance, as well as the relationship of indoor CO₂ concentrations to other indoor pollutants has been studied. Monitoring indoor CO₂ concentrations with sensors and sensor systems can be a useful tool in assessing building ventilation and indoor air quality issues related to building occupants.

5.3 This test method may be used to evaluate the performance of CO₂ sensors or sensor systems used as occupant or user feedback devices and for CO₂ sensor-facilitated demand control ventilation systems. These devices and systems may improve indoor air quality through dynamic response to CO₂ and pollutant concentrations, as well as increased indoor air quality awareness.

5.4 CO₂ sensors and sensors systems can include components, such as pumps, that cause the sensor or sensor system to sample actively rather than passively. The presence of these components can sometimes vary in impact even between sensors of the same model number. The presence of these components can affect the ability of sensors and sensor systems to measure and respond to changes in CO₂ concentrations. This test method does not evaluate this ability, or lack thereof.