Automated System for Measuring Air-exchange Rate and Radon Concentration in Houses

Abstract

An automated system for continuously measuring the air exchange rate and 222Rn concentration in an occupied residence was developed. The air exchange rate was measured over 90 min intervals by tracer gas decay using SF6 as the tracer gas. The Rn-concentration was measured over 3 h intervals using a flow-through scintillation cell. Temperatures at up to 7 points were measured every half hour. A microcomputer system controlled the measurements, performed preliminary data analysis and logged the data and results. Continuous measurement of ventilation rate and Rn concentration permitted the effective Rn source magnitude to be calculated as a function of time. The 1st field application of this system was a study in Rochester, NY [USA], of residential air exchange rates and indoor air quality. For the 8 houses monitored, the mean values over 4-14 day periods ranged from < 0.2-2.2 pCi/l for Rn, 0.22-1.16/h for air exchange rate and < 0.05-0.75 pCi/l per h for Rn source magnitude.