It has been noted in previous survey reports by the Department, that basements with sumps generally have higher radon concentrations. The radon concentration can usually be lowered by covering the sump. The Department found it surprising that the average mobile home radon concentration was almost as high as the concentration in conventional homes. The reasons for mobile homes having such high concentrations of radon are unknown at this time. Older homes generally have crawl spaces for small houses and basements for larger houses.
Some houses are a combination of all three types.
Following Federal guidelines, the Department categorized the buildings such that most buildings were contained in the first four types. The most popular other type of building selected was multifamily. The most used rooms were the living room, bedroom, family room, and unfinished basement. Major contributors to variance are the county, the city, the building, and the sump. Figure 5 indicates the data is log normal except for lower concentrations.