Under the federal Clean Air Act, 42 U.S.C. § 7401 et seq., and the Tennessee Air Pollution Control Act, T.C.A. § 68-201-101, et seq., certain counties may be required by the Tennessee Air Pollution Control Board to implement a motor vehicle inspection and maintenance program in order to attain or maintain compliance with national ambient air standards if

(a) the county has been designated by the United States Environmental Protection Agency as a nonattainment county and has more than 50,000 registered vehicles, or

(b) is a former nonattainment county with more than 50,000 registered vehicles that is under a maintenance plan designed to continue to meet the national ambient air standards, or

(c) the county contributes significantly to nonattainment in another county and has more than 60,000 registered motor vehicles.  

The Air Pollution Control Board may issue waivers consistent with federal and state law.  Also, such a program may exist in counties for which the county legislative body has adopted a resolution that establishes an inspection and maintenance program consistent with the programs required by the state.  All counties implementing a vehicle inspection and maintenance program may only charge fees that are directly related to the county's cost of establishing and maintaining the program.  Such programs must follow rules established by the Tennessee Air Pollution Control Board. Inspections will occur annually in conjunction with vehicle registration renewal.  2004 Public Chapter 926; T.C.A. §§ 55-4-128, 55-4-130.