N.C. Gen. Stat. § 20-37.20B
Following receipt of notice pursuant to G.S. 20-37.19(c) of a positive test in an alcohol or drug test, the Division shall notify the driver of the pending disqualification of the driver to operate a commercial vehicle and the driver's right to a hearing if requested within 20 days of the date of the notice. If the Division receives no request for a hearing, the disqualification shall become effective at the end of the 20-day period. If the driver requests a hearing, the disqualification shall be stayed pending outcome of the hearing. The hearing shall take place at the offices of the Division of Motor Vehicles in Raleigh. The hearing shall be limited to issues of testing procedure and protocol. A copy of a positive test result accompanied by certification by the testing officer of the accuracy of the laboratory protocols that resulted in the test result shall be prima facie evidence of a confirmed positive test result. The decision of the Division hearing officer may be appealed in accordance with the procedure of G.S. 20-19(c6).
N.C. Gen. Stat. § 20-37.20B