When South Carolina Requires an Ignition Interlock Device
What an ignition interlock device does and when South Carolina requires one
An ignition interlock device is a small machine connected to your vehicle's ignition system that measures your breath alcohol content before the engine will start. If the device detects alcohol above a set limit, the engine will not turn on. South Carolina requires one after certain DUI convictions, and in some cases before trial if you want to keep driving.
The state mandates an interlock device for anyone convicted of driving under the influence (DUI), regardless of whether it was a first offense or a repeat conviction. You may also be ordered to install one as a condition of bond or pre-trial release if you were arrested for DUI and want to continue driving while your case is pending.
The device stays in your vehicle for a set period determined by the court — typically one to three years depending on your conviction history and the judge's order. During that time, you pay for installation, monthly monitoring, and removal. The cost is your responsibility, not the state's.
Key Takeaways
- South Carolina requires an ignition interlock device after a DUI conviction, and the length of time you must use it depends on whether it is your first offense or a repeat conviction.
- You may be ordered to install a device before trial if you want to keep driving while your DUI case is pending, even if you have not yet been convicted.
- The device must be installed by a certified provider on the South Carolina Department of Alcohol and Other Drug Abuse Services approved list.
- You are responsible for all costs: installation, monthly monitoring fees, and removal, which typically total several hundred dollars over the required period.
- Tampering with, removing, or bypassing the device is a separate criminal offense and will extend your interlock requirement.
How long you must use the device based on your conviction
The length of your interlock requirement depends on your DUI history. For a first DUI conviction, South Carolina requires the device for a minimum of six months. If you have prior DUI convictions within the past ten years, the requirement increases: two years for a second offense within ten years, and three years for a third or subsequent offense.
The court order will specify the exact start and end dates. The clock typically begins when the device is installed, not when you are convicted. If you are ordered to install it before trial as a condition of bond, that time may count toward your total requirement — but this depends on the judge's order, so confirm with your attorney or the court.
If you are caught driving without the device during the required period, or if the device records a violation (a failed breath test or a tamper alert), the court can extend your requirement. Some judges add three to six months for each violation.
Finding a certified provider and getting the device installed
You must use a provider certified by the South Carolina Department of Alcohol and Other Drug Abuse Services. The state maintains a list of approved vendors; ask your attorney, the court clerk, or the probation office for the current list, or contact the Department of Alcohol and Other Drug Abuse Services directly at 803-896-5555.
Once you have the court order, contact a certified provider to schedule installation. The appointment usually happens within one to two weeks. Bring your vehicle, proof of insurance, and the court order. Installation takes about one to two hours and costs between $100 and $200, depending on the provider.
After installation, you will receive a schedule for monthly monitoring appointments. These are brief visits where the provider downloads data from the device and checks that it is functioning correctly. You must keep these appointments or face additional penalties.
How the device works and what happens during a test
Before you start your vehicle, the interlock device will prompt you to provide a breath sample. You blow into the mouthpiece for about five seconds. The device analyzes your breath alcohol content and either allows the engine to start or prevents it from starting.
The state sets the threshold at 0.02 percent blood alcohol content — lower than the legal driving limit of 0.08 percent. This means even a small amount of alcohol will trigger a fail. If you fail, the device will not allow the engine to start, and the failure is recorded and reported to your monitoring provider.
Some devices also require rolling retests — additional breath samples while you are driving. If you fail a rolling retest, the device will not shut off your engine immediately, but it will log the violation and may trigger your horn and lights to alert you to pull over safely. The violation is reported at your next monitoring appointment.
Costs and what to expect to pay
The total cost of an ignition interlock device over the required period varies by provider but typically ranges from $1,200 to $2,500. This breaks down roughly as follows: installation ($100 to $200), monthly monitoring fees ($60 to $100 per month), and removal ($100 to $150).
You are responsible for all these costs. The state does not cover them, and they are separate from any fines or court costs imposed as part of your DUI sentence. Some providers offer payment plans, so ask about that option when you call to schedule installation.
If you cannot afford the device, inform the court. Some judges have discretion to order the state to cover costs for defendants with very low income, though this is rare. Your attorney can request a hearing to ask the judge to consider this.
What happens if you tamper with or remove the device
Tampering with, removing, or attempting to bypass the ignition interlock device is a separate criminal offense in South Carolina. This includes disconnecting wires, using a different vehicle, having someone else blow into the device, or any other method to circumvent it.
If you are caught tampering with the device, you face criminal charges, additional fines, jail time, and an extended interlock requirement — often adding one to three years to your original order. You may also lose your license entirely and face other penalties related to your original DUI case.
The device records all attempts to start your vehicle and all breath tests. Your monitoring provider reports this data to the court and to your probation officer (if you are on probation). Violations are taken seriously.
Driving with the device and what you need to know
Once the device is installed, you can drive normally, but you must always be prepared to provide a breath sample when prompted. Keep the device clean and dry — moisture or food particles can affect its accuracy. Do not eat, drink, or smoke immediately before blowing into it, as residue can trigger a false positive.
If you are taking medication or using mouthwash, be aware that some products contain alcohol and may cause a failed test. Ask your doctor or pharmacist whether any medications you take contain alcohol, and inform your monitoring provider if you are taking them.
You must keep your vehicle in good working order and bring it to all scheduled monitoring appointments. If your vehicle breaks down or is in the shop, contact your monitoring provider immediately — you may be able to arrange a temporary device transfer or a brief extension of your appointment deadline.
Frequently Asked Questions
Can I drive someone else's car instead of using the interlock device?
No. The court order requires you to use the device in any vehicle you operate. If you are caught driving a vehicle without the device during your required period, you are in violation of the court order and can face additional criminal charges, jail time, and an extended interlock requirement.
What if I blow into the device and it says I failed, but I have not had any alcohol?
False positives can happen due to residue from food, mouthwash, or certain medications. If you believe the result is inaccurate, contact your monitoring provider immediately and explain what you consumed or took before the test. The provider can note this in your file. If violations continue, ask your attorney about requesting a hearing to challenge them.
Do I have to keep the device if I move out of South Carolina?
Yes. The court order remains in effect regardless of where you live. You must find a certified interlock provider in your new state and transfer the device. Contact your monitoring provider in South Carolina before you move to arrange the transfer and confirm that your new provider is certified.
Can the interlock requirement be removed early?
Only the court can remove or shorten the requirement. You can petition the judge to remove it early, but this is rare and usually only granted if you have a clean record during the required period with no violations or failed tests. Your attorney can file the motion on your behalf.
What happens after the device is removed?
Once the required period ends, contact your monitoring provider to schedule removal. The provider will uninstall the device and provide you with a removal certificate. Keep this certificate for your records. After removal, you can drive normally without any interlock restrictions, though your DUI conviction remains on your driving record.