N.C. Gen. Stat. § 20-128: Exhaust system and emissions control devices.

(a) No person shall drive a motor vehicle on a highway unless such motor vehicle is equipped with a muffler, or other exhaust system of the type installed at the time of manufacture, in good working order and in constant operation to prevent excessive or unusual noise, annoying smoke and smoke screens.

(b) It shall be unlawful to use a "muffler cut-out" on any motor vehicle upon a highway.

(c) No motor vehicle registered in this State that was manufactured after model year 1967 shall be operated in this State unless it is equipped with emissions control devices that were installed on the vehicle at the time the vehicle was manufactured and these devices are properly connected.

(d) The requirements of subsection (c) of this section shall not apply if the emissions control devices have been removed for the purpose of converting the motor vehicle to operate on natural or liquefied petroleum gas or other modifications have been made in order to reduce air pollution and these modifications are approved by the Department of Environmental Quality. (1937, c. 407, s. 91; 1971, c. 455, s. 1; 1983, c. 132; 1989, c. 727, s. 9; 1997-443, s. 11A.119(a); 2000-134, s. 6; 2015-241, s. 14.30(u).)