RADON MITIGATION WITH PRESSURE-CONTROLLED MECHANICAL VENTILATION

Effective ventilation and positive or low negative pressure indoors ar e suggested to achieve low indoor radon levels. The aim of this study was to develop and to test equipment which makes it possible to achiev e simultaneously effective ventilation and minimum indoor-outdoor pres sure difference. The unit included mechanical supply and exhaust air f ans, a heat-exchanger and a pressure control unit in direct digital co ntrol (DDC), which continuously adjusted airflows based on the pressur e difference transmitter information. Indoor radon level decreased fro m 501 +/- 95 Bq/m3 to 202 +/- 54 Bq/m3 after two weeks of the equipmen t's installation during winter conditions. The arithmetic week average of indoor radon level was 135 Bq/m3 from May to August. When the set value of pressure difference adjustment was slightly positive (0.2 Pa) and in-out temperature difference was small in August, the minimum le vel (38 +/- 28 Bq/M3) was obtained