How much does an ignition interlock device cost?

Costs include installation, monthly monitoring, calibration, and removal fees that vary by provider and state. Financial assistance may be available for qualifying offenders.

What happens if I fail an IID breath test?

A failed startup test prevents the engine from starting and is logged. Failed rolling retests while driving are also logged. Violations can extend the IID period and may trigger additional legal consequences including [def:probation] violations.

Can I drive a different vehicle without the IID?

No. During the IID period, you are required to have the device installed on every vehicle you operate [§ 20-17.8]. Driving a vehicle without an IID when one is required is a violation that can result in additional penalties.

Topic guideUpdated 2026-02-27

North Carolina Ignition Interlock — Requirements & Costs

When interlock may be required and practical steps.

An ignition interlock device (IID) is a breathalyzer wired into your vehicle's ignition system. It prevents the engine from starting if it detects alcohol on your breath above a preset threshold §20-17.8. In North Carolina, IID requirements are a central part of DWI consequences.

When North Carolina requires an IID §20-17.8

required if BAC ≥ 0.15, prior DWI within 7 years, or sentenced at Aggravated Level 1.

How long the IID must remain installed

1 year for 1-year revocation; 3 years for 4-year revocation; 7 years for permanent revocation.

How the device works in practice

Installation

A certified provider installs the device in each vehicle you operate (not just the vehicle involved in the arrest). You pay for installation and ongoing monitoring fees.

Starting the vehicle

Before starting the engine, you breathe into the device. If the sample is below the preset threshold, the engine starts normally. If it is above the threshold, the engine will not start, and the event is logged.

Rolling retests

While driving, the device will periodically prompt you to provide another breath sample. This prevents someone else from providing the startup sample. Failure to provide a sample or failing a rolling retest is logged and can trigger a violation.

Calibration and data download

The device must be serviced at regular intervals set by the provider. The provider downloads the data log, recalibrates the device, and reports any violations to the monitoring authority.

Violations and extensions

Common violations that can extend the IID period or trigger additional consequences:

Failed startup tests (BAC above threshold)
Failed rolling retests
Missed calibration appointments
Tampering with or attempting to circumvent the device
Operating a vehicle without an IID when one is required

Costs

IID costs are borne by the offender and include:

Installation fee
Monthly monitoring/rental fee
Removal fee
Calibration fees (may be included in monthly rental or charged separately)

✓Some states, including North Carolina, offer financial assistance programs for offenders who cannot afford IID costs. Ask the court or your attorney about indigency provisions.

The IID as a path back to driving

While the IID is a restriction, it is also the mechanism that allows many offenders to resume driving sooner than they would under a full suspension. In North Carolina, Limited Driving Privilege (LDP) available after first 10 days of the 30-day civil revocation for essential purposes (work, school, medical). The 1-year refusal revocation under §20-16.2 is separate from and in addition to this 30-day civil revocation.. Complying fully with IID requirements — no violations, on-time calibration — is the fastest path to full reinstatement.

Prepare for Your Consultation

Quick checklist (DUI)

Dates matter. If you have paperwork, bring it.

Citation or arrest

paperwork

Court dates

or hearing notices

Your timeline of events

(brief)

General preparation tips only. Deadlines vary by facts and jurisdiction.

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