"EPA/600-SR-92-059." "June 1992." Caption title. At head of title: Project Summary.

Natural basement ventilation has always been recommended as a means of reducing radon levels in houses. However, its efficacy has never been documented. It has generally been assumed to be a very inefficient mitigation strategy since it was believed that dilution was the mechanism by which radon levels were reduced. natural ventilation has been studied in two research houses during both the summer cooling season and the winter heating season. Ventilation rates, environmental and house operating parameters, and radon levels have been monitored; it can be definitively concluded from radon entry rate calculations that natural ventilation can reduce radon levels two ways; (1) by simple dilution, and (2) although less obvious, by providing a pressure break which reduces basement depressurization and thus the amount of radon-contaminated soil gas drawn into the house. Thus, basement ventilation can be a much more effective ventilation strategy than was previously believed. It might be especially useful in houses with low radon concentrations (of the order of 10 pCi/L) or those with low levels that cannot be mitigated cost-effectively with conventional technology.