Advancing understanding of temporal performance and behaviour in consumer-grade electronic radon monitors

Consumer-grade electronic radon monitors (ERMs) are becoming increasingly popular, yet evidence of their performance remains largely based on short-term testing of a limited number of devices. This study evaluated nine models of consumer-grade ERMs over a 3-month exposure period in a radon chamber to assess accuracy, precision, stabilization, drift, and temporal behaviour. Absolute mean difference (AMD) improved over time, with all devices achieving <25% AMD after 1 month. Detector technology was the primary determinant of temporal performance. Ionization chamber-based devices stabilized within 24 h but exhibited a slight positive bias, whereas photodiode-based devices required several weeks to stabilize yet produced more accurate long-term averages. Time-series analyses indicated that photodiode-based devices exhibited signatures of internal data processing that suppressed short-term variability. Overall, the ERMs evaluated provided reliable integrated measurements over test periods consistent with long-term testing guidance. These findings support the development of performance standards, certification programs, and public guidance.