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RE-ENTRAINMENT AND DISPERSION OF EXHAUSTS FROM INDOOR RADON REDUCTION SYSTEMS: ANALYSIS OF TRACER GAS DATA
Henschel, D. RE-ENTRAINMENT AND DISPERSION OF EXHAUSTS FROM INDOOR RADON REDUCTION SYSTEMS: ANALYSIS OF TRACER GAS DATA. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-96/019.
The paper discusses two tracer gas studies, to quantify the extent to which exhaust gases from indoor radon reduction systems are re-entrained into pitched-roof houses (exposing persons indoors), and the manner in which the exhausts disperse outdoors (exposing persons outside the house). hese studies included a wind tunnel physical modeling project and a field project. ased on wind-tunnel testing with grade level exhaust, the mean outdoor concentrations contributed by the exhaust on the exhaust side of the house may average about 7 times those with eave exhaust, and about 25-50 times those with exhaust midway up the roof slope (as with an indoor exhaust stack having a fan in the attic). id-roof exhaust is always better than the other two configurations in dispersing exhaust gases- eave exhaust is better than grade-level exhaust, except when the exhaust is on the upwind side of the house. ithin 15-24 m of the house, radon concentrations from the exhaust will almost always have dropped to a fraction of the ambient average, even with exhaust levels of 37,000 Bq/cu m. Results of re-entrainment field testing, limited to one house, suggest that--if active soil depressurization systems exhaust at grade level, with no stack--the indoor air concentrations resulting from re-entrainment may be 3-9 times higher than if the discharge were above the eave, near the roof overhang.