S.C. Code Ann. § 56-5-2941
(A) Except as otherwise provided in this section, in addition to the penalties required and authorized to be imposed against a person violating the provisions of Section 56-5-2930, 56-5-2933, or 56-5-2945, or violating the provisions of another law of any other state that prohibits a person from driving a motor vehicle while under the influence of alcohol or other drugs, the Department of Motor Vehicles must require the person, if he is a subsequent offender and a resident of this State, to have installed on any motor vehicle the person drives an ignition interlock device designed to prevent driving of the motor vehicle if the person has consumed alcoholic beverages. The Department of Motor Vehicles may waive the requirements of this section if it finds that the offender has a medical condition that makes him incapable of properly operating the installed device.
The length of time that an interlock device is required to be affixed to a motor vehicle following the completion of a period of license suspension imposed on the offender is two years for a second offense, three years for a third offense, and the remainder of the offender's life for a fourth or subsequent offense. Notwithstanding the pleadings, for purposes of a second or a subsequent offense, the specified length of time that an interlock device is required to be affixed to a motor vehicle is based on the Department of Motor Vehicle's records for offenses pursuant to Section 56-5-2930, 56-5-2933, or 56-5-2945.
(O) Only ignition interlock devices certified by the Department of Probation, Parole and Pardon Services may be used to fulfill the requirements of this section.