An ignition interlock device (IID) is a small breathalyzer wired into your vehicle's ignition system. You blow into the device before starting the car and again at random intervals while driving. If your breath alcohol concentration exceeds the device's set limit (usually 0.02–0.025), the engine will not start and the failed test is logged and reported to the monitoring authority. IIDs are required after most DUI convictions in all 50 states.
How Long Is the IID Required?
First offense: 6–12 months in most states (mandatory minimum 12 months in Arizona, California, Texas, and others). Second offense: 1–3 years. Third or subsequent offense: 3 years to lifetime.
The term begins on the date of installation, not the date of conviction. Removing the device early without authorization or driving a non-IID vehicle voids credit and restarts the term.
What It Costs
Installation: $70–$150 one-time. Monthly lease and monitoring: $60–$100. Calibration visits (every 30–60 days): $20–$50 each. Removal: $50–$100.
Total annual cost typically runs $1,000–$1,500, paid entirely by the driver. A small number of states offer indigent assistance programs — ask your monitoring authority before installing.
How the Device Works
Initial test: blow into the device before starting the engine. The car will not start if BrAC exceeds the set limit. Rolling retests: the device requires another sample every 5–45 minutes while driving. Failed rolling retests cause the lights and horn to activate (the engine will not shut off) until you safely pull over.
Most modern IIDs include a camera that photographs the person blowing into the device, GPS logging of every event, and tamper sensors. Data is transmitted wirelessly to the monitoring center every time you visit a calibration appointment.
Common Violations
Failed start attempt (any reading above the limit). Missed rolling retest. Bypass or circumvention attempts (disconnecting the device, using compressed air, having someone else blow). Tampering with the camera or wiring. Missed calibration appointment (devices auto-lockout after the calibration window).
Any of these are reported to the court or DMV within 24 hours and can extend the IID period, revoke probation, and result in additional jail time.
Top IID Providers
Smart Start, Intoxalock, LifeSafer, Draeger Interlock, Guardian Interlock, and Monitech are the largest national providers. Pricing is fairly uniform; choose based on local installation locations and customer service ratings.
The device must be on your state's certified-provider list. Using a non-certified device will not satisfy the court order.
Getting the IID Removed
Once your court-ordered period ends and you have a clean compliance record (typically the final 90–180 days violation-free), the monitoring authority issues a removal authorization. Bring the authorization to your provider; they will deinstall the device and certify removal back to the DMV.
Do not have the device removed without authorization — most states will reinstate the suspension and add additional months.
Frequently Asked Questions
Will mouthwash trigger the IID?
Yes — alcohol-based mouthwashes can register a positive. Wait at least 15 minutes after using mouthwash and rinse with water before blowing.
Who pays for the IID?
The driver pays all installation, monthly lease, and calibration fees. A handful of states offer indigent assistance programs that reduce or waive monthly fees for low-income drivers.
Can someone else blow into my IID?
It is a separate criminal offense (circumvention) for both parties. Modern devices include cameras and rolling retests that almost always detect circumvention.
What happens after a failed IID test?
The vehicle will not start, the event is logged with photo and GPS, and the report is transmitted to your monitoring authority within 24 hours. Repeated failures extend the IID period or revoke probation.
Do I need an IID on every vehicle I drive?
Yes. The court order applies to you, not a specific car. Driving any vehicle without an IID during your monitoring period is a separate criminal offense.
What if my car battery dies and the device resets?
Modern IIDs retain memory through battery disconnects. Your provider will note the disconnect at your next service appointment; brief, one-time disconnects are not violations.
Related DUI guides
Safety notice and legal disclaimer
Never drive after drinking or using impairing substances. If you have been arrested or charged with a DUI/DWI, contact a licensed attorney in your state immediately — administrative license deadlines often run within days of arrest.
This page is general legal information published by the DUIGuide.us editorial team, not legal advice, and it does not create an attorney-client relationship. Laws change frequently; verify statutes and court rules with official state sources or licensed counsel. See our editorial policy and full disclaimer.