Measurements of radon and radon daughters in 11 buildings in five states, using active or passive solar heating showed no significant increase in concentration over the levels measured in buildings with conventional heating systems. Radon levels in two buildings using rock storage in their active solar systems exceeded the U.S. Nuclear Regulatory Commission's 10 CFR 20 limit of 3 pCi/l for continuous exposure. In the remainder of the buildings, radon concentrations were found to be at levels considered to be normal. It appears that the slightly elevated indoor radon concentrations results from the local geological formations and from the tightening of the buildings rather than as a result of the solar heating technology.
Radon and radon daughter measurements in solar energy conservation buildings
Environmental Measurement Laboratory, USA, Department of Energy, Report no. DOE/EML-407, New York, 1982, NTIS, 14pp, 4 figs, 1 tab, 15 refs. #DATE 00:00:1982 in English