Air ions as indicators of short-term indoor radon variations.

Diurnal variations in the air ion concentration are subject to changes in the radon concentration. In this experiment, the air ion and radon concentrations were simultaneously measured using two air ion detectors and two continuous radon detectors. The results of the indoor measurements revealed a strong correlation between the concentrations of positive air ions and radon (with a correlation coefficient greater than 0.9). The radon-to-ion concentration ratio changes with an increase in the radon concentration from a linear to a square-root relation. This correlation provides a means of using air ion measurements as a high-confidence indicator of changes in the radon concentration, especially for short-term measurements on the order of seconds or minutes, which is too short a measurement interval for conventional radon monitors. The use of air ions as an indicator of changes in radon concentration allows for investigation of the behavior of indoor radon and also allows radon to be used as a tracer gas for air mass exchange.