Will I Have to Have a “Blow Box” in My Car if Convicted of an OBX DWI?
Updated September 30, 2026, with the current ignition interlock rules.
When North Carolina Requires an Ignition Interlock
An ignition interlock, often called a “blow box,” is a breath-testing device wired into a vehicle’s ignition. Under N.C.G.S. Section 20-17.8, when DMV restores a license after a DWI conviction, it must require an interlock if any of these apply:
- Your alcohol concentration was 0.15 or more.
- You have another impaired driving conviction for an offense within the seven years before this one.
- You were sentenced at Aggravated Level One.
The requirement also applies after a habitual impaired driving conviction and after certain death or serious injury by vehicle convictions.
How Long the Interlock Lasts
| Original revocation | Interlock requirement after restoration |
|---|---|
| One year | One year |
| Four years | Three years |
| Permanent | Seven years |
What the Restriction Requires
- You may drive only vehicles equipped with a working, approved ignition interlock.
- You must personally activate the interlock before driving.
- You may not drive with an alcohol concentration of 0.02 or more.
- You must designate the vehicles you own and drive, and have them equipped.
Older versions of the law used different alcohol limits for interlock restrictions. The current limit is 0.02.
Interlock and Limited Driving Privileges
An interlock can also be a condition of a limited driving privilege. For a Level Two sentence, a limited privilege is available only if the alcohol concentration was below 0.15, and it always requires an interlock. At Levels Three through Five, a driver with a concentration of 0.15 or more can get a limited privilege with an interlock. See DWI sentencing levels.
Live in another state? See out-of-state DWI in the Outer Banks.
Talk to an Outer Banks DWI Lawyer
Whether you will need an interlock, and for how long, depends on the test result, your record, and how your case is resolved. Learn more about DWI defense in Dare and Currituck County.
Charged with DWI in Dare or Currituck County? Call or text Donahue Defense at 252-715-5785.
This article is general information about North Carolina law, not legal advice for your situation.