If you’ve been convicted of a DUI, you may be required to install an ignition interlock device (IID) as a condition for regaining your driving privileges. These small devices can seem intimidating at first, but they are a common legal tool to prevent repeat offenses and promote safer roads.
This guide will explain what ignition interlock devices are, how they work, who’s required to use them, and what to expect in terms of cost, maintenance, and legal responsibilities.
What Is an Ignition Interlock Device?
An ignition interlock device is a breathalyzer installed in your vehicle that prevents the engine from starting if it detects alcohol on your breath. Before you can start your car, you must blow into the device. If your blood alcohol concentration (BAC) is above the pre-set limit (usually 0.02%), the car will not start.
IIDs are designed to:
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Deter repeat DUI offenses
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Allow DUI offenders to keep limited driving privileges
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Promote road safety
They’re typically required for a certain period after a DUI conviction, particularly in first-time offenses involving high BACs or multiple DUI offenses.
How Does an Ignition Interlock Device Work?
The process is straightforward:
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Blow Test Before Starting – You’ll blow into the mouthpiece to test your BAC. If you’re under the limit, the engine starts.
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Rolling Retests – While driving, the IID will require periodic breath samples to ensure continued sobriety. You’ll have a short time window to provide the sample safely.
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Data Recording – The device logs all test results, including test attempts, BAC levels, engine start/stop times, and any tampering or missed tests. This data is sent to your monitoring authority—typically the DMV or a probation officer.
Who Is Required to Use an IID?
Laws vary by state, but ignition interlock devices are often mandatory for:
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First-time DUI offenders (especially if BAC was 0.08% or higher)
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Repeat DUI offenders
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Offenders who refused chemical testing
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Drivers involved in DUI-related crashes
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Individuals seeking a restricted or hardship license
Some states have mandatory interlock laws, requiring all DUI offenders—even first-timers—to install an IID for a minimum period.
How Long Must You Use an Ignition Interlock?
The required duration varies depending on the state and the offense. Common timelines include:
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First offense: 6 months to 1 year
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Second offense: 1 to 2 years
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Third or more: 2+ years or permanent in severe cases
Violations, such as failed tests or tampering, can extend your IID period or lead to license suspension.
How Much Does an Ignition Interlock Device Cost?
Costs can vary based on your location and provider, but here’s a general breakdown:
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Installation fee: $70–$150
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Monthly rental/monitoring: $60–$100
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Removal fee: $50–$100
Over a 6-month period, you could expect to pay $500–$1,000 out of pocket.
Some states offer financial assistance programs for low-income offenders to help cover these expenses.
What Happens If You Fail a Test?
Failing a test (i.e., blowing over the limit) can have serious consequences:
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Your car won’t start
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The device will log the failed attempt
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Multiple failed attempts may lock you out for a period
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Violations are reported to the authorities, which can trigger probation violations, license suspension, or extended IID requirements
Tampering with or trying to bypass the device is considered a criminal offense in many states.
Maintenance and Calibration Requirements
IIDs must be calibrated and maintained regularly, typically every 30 to 60 days. You’ll visit an authorized service center where:
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The device is inspected for tampering
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Data is downloaded and reviewed
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Calibration is adjusted to ensure accurate readings
Failure to appear for required maintenance may result in the device being locked or your license being suspended again.
How Does the IID Affect Your Driving and Routine?
At first, using an ignition interlock device can feel invasive, but most users adapt quickly. Things to keep in mind:
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Always leave extra time before driving in case of retests
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Keep your mouth clean—mouthwash, gum, or certain foods can trigger false positives
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Rolling retests will occur during longer trips, so avoid eating, drinking, or being distracted when prompted
Can You Remove the Device Early?
In some states, if you demonstrate full compliance (no violations, all maintenance done on time), you may qualify for early removal. However, most programs require a minimum term before this is possible.
Always follow your court or DMV’s guidance and avoid premature removal without approval, which can result in license revocation or criminal charges.
Conclusion
An ignition interlock device is more than just a piece of equipment—it’s a critical part of getting your driving privileges back after a DUI. While it may seem inconvenient, it’s also a step toward rebuilding trust with the court system and maintaining public safety.
Understanding how the device works, what’s expected of you, and how to stay compliant will make the process smoother—and help you avoid further penalties.
