||Cohen (S.) and Associates, Inc., McLean, VA. ;Colorado State Univ., Fort Collins. Dept. of Civil Engineering.;Environmental Protection Agency, Research Triangle Park, NC. Air and Energy Engineering Research Lab.
A study has been completed which physically modeled, in a wind tunnel, the dispersion of exhaust plumes from active soil depressurization (ASD) radon mitigation systems in houses. The wind tunnel testing studied the effects of three different exhaust locations: midway up the roof slope, simulating an ASD stack interior to the house; at the eave, simulating an exterior stack; and grade-level exhaust (no stack). Plume dispersion effects were studied using both qualitative smoke visualization and quantitative tracer gas techniques, as the following variables were systematically varied: house height; roof pitch; wind direction; wind speed; and exhaust velocity. The tracer gas results show that grade-level exhausts consistently result in the highest tracer concentrations against the face of the house, although these concenrations may not be serious if exhaust concentrations are low. The wind tunnel physical modeling was supplemented by analytic and numeric modeling, to determine how well the analytic and numeric models reproduced the wind tunnel results. Existing analytic models over-predicted the exhaust gas concentrations that would be seen against the face and roof of the house, and downwind.