Sensors

Indoor air quality sensors measure specific pollutants or environmental conditions, such as carbon dioxide, particulate matter, temperature, and humidity. A monitor may contain several sensors and display or record their readings.

These measurements help identify changes in indoor conditions and assess the effects of ventilation, air cleaning, and everyday activities. Each monitor measures only the parameters it is designed to detect, so no single reading provides a complete picture of indoor air quality.

Sensor Types and Limitations

Parameter	Common Sensing Method	Uses and Limitations
Carbon dioxide (CO2)	Infrared sensing, commonly non-dispersive infrared (NDIR).	Helps assess ventilation in occupied spaces. Readings depend on occupancy, outdoor CO2, and air distribution. CO2 does not indicate all indoor pollutants.
Particulate matter (PM2.5 and PM10)	Optical sensors estimate particle concentrations from scattered light.	Useful for tracking changes related to cooking, smoke, and outdoor particles. Results depend on particle properties and humidity; sensors do not identify particle composition.
Volatile organic compounds (VOCs)	Many consumer monitors use metal oxide sensors to produce a VOC index or estimated total VOC (TVOC) value.	Useful for detecting changes in gas mixtures. These readings generally do not identify individual chemicals or establish their health risk.
Carbon monoxide (CO) and nitrogen dioxide (NO2)	Electrochemical sensors are commonly used.	Monitor specific combustion-related gases. Sensitivity to other gases and environmental conditions can affect results.
Temperature and relative humidity	Electronic temperature and humidity sensors.	Describe thermal and moisture conditions. Readings can be affected by sunlight, nearby heat sources, and heat generated inside the monitor.

Safety note: A general IAQ monitor does not replace a certified carbon monoxide alarm or smoke alarm.

For guidance on understanding concentrations and comparing results with guidelines, see Interpreting the Data.

Choosing a Sensor or Monitor

Choose equipment according to the purpose of monitoring. EDIAQI's monitoring guidelines cover technical and practical factors such as performance, maintenance, usability, and data access.

• Parameters: Check that the device measures the pollutants or conditions you need. Distinguish directly measured concentrations from estimated values and indices.
• Performance: Look for stated accuracy, measurement range, response time, and independent testing under relevant conditions.
• Usability: Consider setup, display readability, power supply, and the needs of the people using the device.
• Maintenance: Check calibration requirements, sensor lifespan, cleaning instructions, and replacement options.
• Data access: Confirm that readings can be recorded and exported in a useful format. Check connection requirements and any subscription costs.

Low-cost monitors can support everyday monitoring and comparisons across rooms. More demanding investigations may require specialist instruments or laboratory analysis. Select equipment with performance appropriate to the intended use.

Calibration and Maintenance

Calibration establishes the relationship between a sensor's readings and a reference. Validation checks whether the measurements are suitable for their intended use.

Follow the manufacturer's instructions for warm-up, cleaning, calibration, and servicing. Keep records of checks and adjustments, and investigate persistent differences between instruments.

Check the calibration requirements for the exact device and arrange recalibration through the provider when needed. EDIAQI's guidelines recommend clear maintenance instructions and information on how to obtain calibration support.

Placement and monitoring duration also affect results. See Measuring IAQ for practical guidance.

Sensor Evaluation in EDIAQI

EDIAQI's Indoor Air Pollution Observation Toolkit describes laboratory and real-world methods for evaluating sensor accuracy, precision, and sensitivity to changing conditions.

Sensor Device Overview

The table summarizes devices described on the linked EDIAQI Wiki pages. Example uses are illustrative, rather than a performance ranking. Parameters and features may vary by model or version.

Device	What It Measures	Example Use	Display and Data Access	Main Feature
Aranet 4	CO2, temperature, relative humidity	Monitoring CO2 in classrooms, offices, and homes	Portable, battery-powered unit with visual CO2 indicators	NDIR CO2 sensing in a portable device.
Awair Omni	Particulate matter, VOCs, CO2, temperature, relative humidity, light, noise	Monitoring several indoor conditions in one location	On-device indicators; Wi-Fi and an account for app features	Combines several measurements in one monitor.
CO2Panel PI	CO2	Fixed monitoring in classrooms and offices	Three-color LED indicator; Wi-Fi for recording and displaying data; continuous power required	Simple visual feedback on CO2 levels.
Dioxcare	CO2, temperature, relative humidity	Portable checks of indoor CO2 conditions	Rechargeable battery, configurable audible alert, limited data storage	Portable NDIR CO2 monitoring.
Extech CO10	Carbon monoxide (CO)	Spot measurements of CO	Battery-powered handheld meter with a backlit display and audible alert	Dedicated CO measurement; does not replace a certified household CO alarm.
Foobot	Particulate matter, VOCs, temperature, relative humidity	Following changes in indoor particles and gases	LED indicator, Wi-Fi connection, and app access	Combined particle and VOC monitoring.
PCE-VOC 1	TVOC and formaldehyde (HCHO)	Screening changes in VOC and formaldehyde readings	Rechargeable handheld meter with a display and visual alert	Displays TVOC and formaldehyde readings; does not identify all individual VOCs.
URADMonitor MODEL A3	PM1, PM2.5, PM10, CO2, VOCs, formaldehyde, ozone, temperature, relative humidity, noise	Continuous monitoring of multiple parameters	Powered fixed station with remote data access; no built-in display	Combines particle, gas, and environmental measurements.
Wöhler CDL 210	CO2, temperature, relative humidity	Recording indoor CO2 and thermal conditions over time	Display, audible alert, data logging, and download to a computer; mains power required for measurements	Stores measurements for later review.

Related Pages

• Measuring IAQ: Measurement approaches, sensor placement, and monitoring duration.
• IAQ Data Management: Organizing, checking, storing, and sharing data, including privacy considerations.
• Interpreting the Data: Understanding readings and comparing results with guidelines.
• IAQ Data Reporting and Visualization: Presenting results through dashboards, reports, and alerts.
• SensorThings API: A standard for exchanging sensor observations between systems.

References

For the wiki's agreed literature sources, see Reading List.