Validating the performance of low-cost IAQ sensors through co-location

Area of Science:

• Environmental Science
• Sensor Technology
• Public Health

Background:

• Consumer-grade indoor air quality (IAQ) sensors offer accessible real-time monitoring.
• Sensor performance can be significantly influenced by environmental conditions.
• Accurate IAQ data is crucial for occupant health and research in the built environment.

Purpose of the Study:

• To comprehensively evaluate the performance of two low-cost IAQ sensors: Airthings View Plus (CO₂) and Air Gradient Pro (CO₂ and PM_2.5).
• To assess the precision and accuracy of these sensors against reference instruments.
• To determine the impact of averaging intervals on sensor performance.

Main Methods:

• Co-location testing of consumer-grade sensors with reference instruments (Graywolf DSII-8 for CO₂, Lighthouse Handheld 3016 for PM_2.5).
• Utilized time-series analysis, linear regression, Pearson correlation, RMSE, Bland-Altman tests, and paired t-tests.
• Evaluated sensor performance at 5-minute and 30-minute sampling intervals.

Main Results:

• Air Gradient demonstrated higher precision (R², Pearson correlation, LoAs) but lower accuracy (bias, RMSE) for CO₂ compared to Airthings.
• Air Gradient showed good performance for PM_2.5 with R²=0.79, ρ=0.69, narrow LoAs (30.1 μg/m³), and low RMSE (5.8 μg/m³).
• Averaging measurements over 30-minute intervals generally improved accuracy and precision for both sensors, though significant differences from reference instruments persisted.

Conclusions:

• Consumer-grade IAQ sensors provide valuable relative trend data but may require calibration for absolute concentration accuracy.
• The Air Gradient sensor is suitable for tracking relative CO₂ changes; calibration is recommended for precise measurements.
• In-situ calibration is essential for ensuring the reliability of low-cost IAQ sensors in long-term monitoring applications.