Homes with Radon Mitigation Systems
The estimated number of homes with operating radon mitigation systems is derived from radon vent fan sales data. The three radon vent fan manufacturers whose sales account for 99% of the market provide the following annual data to the Environmental Protection Agency (EPA): the number of radon vent fans sold; their potential non-radon application or use; and estimates of their useful life.
U.S. Homes Above EPA's Radon Action Level. Available at: http://cfpub.epa.gov/eroe/index.cfm?fuseaction=detail.viewMeta&ch=46&lShowInd=0&subtop=343&lv=list.listByChapter&r=224027.