Ventilation Rate and Source Emanation Rates by Measurement of Induced Radon Time-dependent Behavior

The use of induced time-dependent Radon-222 behavior, to determine source rate magnitudes, ventilation rates (air change rates) and other parameters that affect Rn-222 and progeny levels and exposure to building occupants, is investigated. Under the conditions of purging the subject space and measuring the build-up (seepage) back into the space, theoretical, normalized equations show aunique, one-to-one correspondence of the Rn-222 andor particulate progeny temporal levels to the air change rate in the space. The Bateman equations have been solved in closed form for Rn-222 and progeny in air and trapped on a filter under these conditions. A total of 28 measurements of Rn progeny time-dependent behavior for two test facilities (one with constant air change rate and one with a constant NIST-calibrated source) and four residential dwellings were made. The results were compared to theory and to air change rate measurements made by anemometer flow rates and by the conventional method (SF6 decay). Over a factor of 2 range in air change rates in the NIST constant source case the agreement with the SF6 method air change rate was within  10.6% S.D. and agreement with the NIST source magnitude of 37.0  1 kBq was within  4.9% S.D. Agreement to within  17.7% S.D. was obtained on determination of air change rates for the residential dwellings. Knowing the airborne concentrations and air change rates, source emanation rate magnitudes are obtained.