In 2005, Michigan enacted legislation requiring the state’s Department of Consumer and Industry Services to promulgate a building code that incorporates the international codes and that is applicable throughout the state. See Mich. Comp. Laws Ann. 125.1504. The Department then incorporated the International Residential Code into the Michigan Residential Code and included IRC Appendix F. The state has since updated the code to incorporate the 2006 version of the IRC, including Appendix F. See Mich. Admin. Code Regs. 408.30401. The state lists nine Michigan counties that are designated as Zone 1 counties (based on the EPA Map of Radon Zones) and thus subject to the radon control requirements in Appendix F.