Colo. Rev. Stat. § 25-7-114.2
No person shall construct or substantially alter any building, facility, structure, or installation, except single-family residential structures, or install any machine, equipment, or other device, or commence the conduct of any such activity, or commence performance of any combinations thereof, or commence operations of any of the same which will or do constitute a new stationary source or a new indirect air pollution source without first obtaining or having a valid construction permit therefor from the division or commission, as the case may be; except that no construction permit shall be required for new indirect air pollution sources until regulations regarding construction permits for such sources have been promulgated by the commission, but in no event shall regulations governing indirect air pollution sources be more stringent than those required for compliance with the federal act and final rules and regulations adopted pursuant thereto. Any emission permit validly issued prior to July 1, 1992, pursuant to section 25-7-114, as said section existed prior to July 1, 1992, and in effect on or after July 1, 1992, shall be deemed to be a valid construction permit issued pursuant to this section. The commission shall designate by regulation those classes of minor or insignificant sources of air pollution which are exempt from the requirement for a permit because of their negligible impact on air quality.
C.R.S. § 25-7-114.2