Speaker
Description
Many Electronic Radon Integrating Monitors (ERIMs) have been developed and retailed over the last decade. ERIMs are targeted to non-professional consumers, are smaller and lighter than an AlphaGUARD, and have a screen and/or mobile application for the display of radon levels. Many of them use a small diffusion chamber with a silicon photodiode for the detection of radon. Some ERIMs could allow a consumer to read their radon concentrations from the device daily or weekly. However, the UKHSA advice is to use it for at least 3 months to account for the diurnal and seasonal fluctuations of indoor radon. Some manufacturers also claim that their devices would not need calibration which is investigated here.
This study investigated the performance of a range of ERIMs (AlphaE, AER Plus, Canary, Corentium Pro, Radon Scout Home, Ramon and Wave) and the UKHSA passive radon detectors. The monitors were placed in a container flushed with nitrogen gas to determine their background readings for 10 days. Then all monitors and passive radon detectors were exposed for 3 months in 2019 and 2022, to 4781 Bq m-3 and 166 Bq m-3 in the UKHSA radon chamber and in a low radon exposure facility, respectively. The reference levels of radon were established with calibrated instruments traceable to a primary radon gas standard.
The performance of the ERIMs were evaluated with the UKHSA intercomparison classification based on the measurement error of the results. This allowed the grading to be based on both the accuracy and precision of the ERIMs. It was found that the performance of most ERIMs became worse when exposed to the radon levels below the UK radon Action Levels. The passive radon detectors were performing very well in both low and high radon levels, their measurement error was less than 10%.
The calibration factors of the ERIMs were measured at the beginning and the end of the experiment, to verify the claim of some manufacturers that ERIMs did not require calibration. The calibration factors were found to have greatly changed over 4 years, with percentage changes ranging from -46.3% to +63.3%.