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North Carolina laws §§20-17.8(a), (b) and (c), §20-179.3(g3) (g5), and §20-17.8(c) govern restricted driving privileges and ignition interlock devices. Currently, this requirement is mandatory if the BAC was greater than 0.15, but this section of the law is only effective until December 1, 2016. So unless the legislature changes the law it will revert back to the 0.16. Also if the person is a second or subsequent offender (within 7 years).
After license restoration, required ignition interlock usage is as follows: 1 year if license revocation was for 1 year; 3 years if license revocation was for 4 years; and 7 years if the license was permanently revoked but can be restored.
Keep in mind there is also a criminal component to the law where if a person is caught tampering or attempting to circumvent the interlock system, they can be charged with a Class 1 misdemeanor.
I hope this helps with your question.