IAQ, radon, measurement, indoor air quality, pollutants
Radon gas is the most deadly indoor air pollutant. In the US it is responsible for over 20,000 deaths per year. Residential exposure is typically the largest portion of a person’s annual exposure, so a great deal of research has been done to understand the pathways that radon can follow to enter a house. Since radon emanates from the ground, it is present in high concentration in soil gas. Recent research on the vapor intrusion of volatile organic compounds from subsurface sources into a test house concluded that the sewer line is an important preferential pathway. Despite the potential for high concentrations of radon in sewers, there have been no studies examining correlations between sewer concentrations and indoor concentrations. One reason may be that it is very difficult to measure radon concentrations in sewers. To address this problem, the author has developed a method for testing radon concentrations in residential sewer connections, and conducted case studies to test and refine the method. The method uses the sewer cleanout cap as an access point, and addresses the problem of condensation from hot water discharge into the sewer system by heating a sampling chamber that holds the radon sampling device. Preliminary results show a large variation in sewer radon concentrations, both temporally and spatially, and a measured range from 1.8 pCi/L (67 Bq/m³) to 1033 pCi/L (38,221 Bq/m³). For context, the US EPA recommends taking action if indoor levels are above 4 pCi/L (148 Bq/m³). Future work will examine correlations between indoor concentrations and sewer gas concentrations.