What an ignition interlock device does
An ignition interlock device is a breath-testing machine wired into your vehicle's ignition system. Before the engine will start, you blow into the device. If it detects alcohol above a set threshold — usually 0.02 percent blood alcohol content — the engine will not turn over. The device records every test, every pass, and every fail, and that record goes to the court or the state agency overseeing your case.
You are required to install one when a court orders it as a condition of keeping your driving privileges after a DUI or DWI conviction. Some states make it mandatory for all convictions; others require it only for repeat offenses or high blood alcohol readings. The device does not remove your license — it lets you drive, but only if you are sober when you start the car.
The installation itself takes about an hour. A certified technician runs wiring from the device to your ignition, steering column, and sometimes your horn or dashboard lights. Once it is installed, you pay a monthly monitoring fee, usually between $60 and $100, depending on your state and the service provider.
Key Takeaways
- A court order specifies which ignition interlock provider you must use and how long you must keep the device installed, typically six months to three years.
- Installation takes about one hour and costs between $100 and $300, with monthly monitoring fees of $60 to $100 after that.
- You must pass a breath test every time you start the car, and the device records all tests for the monitoring agency to review.
- Tampering with, bypassing, or failing repeated breath tests can result in license suspension and additional criminal penalties.
- The device works in all weather and all vehicle types, though installation in some older or specialty vehicles may cost more.
Finding an approved provider in your state
Your court order will name the specific ignition interlock provider you must use, or it will tell you to contact your state's Department of Motor Vehicles or equivalent agency for a list of approved vendors. Do not choose your own provider — using an unapproved one can result in your license being suspended even if you complete the program otherwise.
Each state maintains its own roster of certified installers. You can find yours by searching "[your state] ignition interlock providers" or by calling your state DMV directly. Common national providers include SCRAM Systems, Smart Start, and Intoxalock, but availability varies by region. Once you have the name of an approved provider, call them to schedule an installation appointment. Most can fit you in within a few days.
Bring your court order, proof of insurance, and a valid ID to the installation appointment. The technician will ask which vehicle you drive most often — if you drive multiple vehicles, you may need to install devices in more than one, depending on your state's rules and your court order.
What happens during installation
The technician will inspect your vehicle's electrical system and run wiring from the interlock device to your ignition switch. The device itself is usually mounted under the dashboard or on the steering column, where you can reach it easily but it is not visible from outside the car. Installation typically takes 45 minutes to an hour.
Before you leave, the technician will show you how to use the device: how to blow into the mouthpiece, how long to blow, and what the lights and sounds mean. They will also explain the rolling retest — after you start the car, the device will ask you to test again at random intervals while you are driving. You have a set amount of time (usually five to ten minutes) to pull over safely and provide a breath sample. Failing a rolling retest or not testing in time counts as a violation.
The technician will give you a schedule for required maintenance checks, usually every 30 days. At each check, the device is recalibrated and the data is downloaded. You must keep these appointments — missing one is treated as a violation and can extend your program or result in license suspension.
Monthly costs and what they cover
Installation fees range from $100 to $300 depending on your vehicle and your state. After that, you pay a monthly monitoring fee, typically $60 to $100. Some providers charge extra for maintenance visits beyond the standard monthly check, and some charge a removal fee when your program ends, usually $50 to $150.
The monthly fee covers the device itself, the data monitoring, and the required calibration visits. It does not cover repairs if the device malfunctions, though most providers warranty their equipment for the duration of your program. If your device breaks down, contact your provider when ready — driving without a working device is a violation, even if the malfunction was not your fault.
Some states offer fee waivers or reductions for people with financial hardship. Ask your provider or your state DMV whether you may have access to. If you cannot afford the monthly fee, you may still be required to have the device, but you can request a hearing to ask the court for a fee reduction.
How the testing process works day to day
Every time you start your car, you will blow into the device for about five to six seconds. The device analyzes your breath and either allows the engine to start or locks it. If you pass, you hear a beep and the ignition engages. If you fail, the device logs the failure and the engine will not start. You can try again after a waiting period, usually 15 to 30 minutes, depending on your device.
While you are driving, the device will ask you to test again at random times — this is the rolling retest. When it prompts you, you have a set window (usually five to ten minutes) to pull over safely and provide another breath sample. If you pass, you can keep driving. If you fail or do not test in time, the device logs a violation. Violations do not stop the car when ready, but they are reported to the monitoring agency and can result in program extension or license suspension.
The device is sensitive to mouth alcohol — mouthwash, cough syrup, or food with alcohol can trigger a false positive. If you know you have used something with alcohol, wait 15 to 20 minutes before testing. If you fail a test you believe was a false positive, ask your provider about a retest or a calibration check.
What violations mean and how they affect your program
A violation is any failed breath test, missed rolling retest, missed maintenance appointment, or attempt to tamper with or bypass the device. The device records all of these and sends the data to the monitoring agency, which reports to the court. One or two violations may result in a warning or a requirement to attend an alcohol education class. Multiple violations can extend your program by months or result in license suspension.
Tampering — disconnecting the device, using a tube to bypass it, or asking someone else to blow into it for you — is a criminal offense separate from your original DUI charge. If you are caught tampering, you face additional criminal penalties, when ready license suspension, and possible jail time. The device is designed to detect tampering: it has sensors that know if it has been disconnected, and it records the identity of the person testing through facial recognition or other means, depending on the model.
If you move out of state or need to transfer your program to a different vehicle, contact your provider and your state DMV before you do. Driving without an active interlock device when one is required is a criminal offense and will result in when ready license suspension.
Removing the device when your program ends
Your court order specifies how long you must keep the device installed — typically six months to three years, depending on your conviction and your state's laws. When that period ends, contact your provider to schedule a removal appointment. The technician will disconnect the wiring, remove the device, and restore your vehicle to its original state. This usually takes 30 to 45 minutes.
After removal, you will receive a letter from the monitoring agency confirming that your program is complete. Take this letter to your state DMV to have your license reinstated to full driving privileges. Some states reinstate automatically once the program ends; others require you to request reinstatement in person or by mail.
Keep all documentation from your program — the installation receipt, maintenance records, and the final removal letter. If you are ever stopped by police and asked about your driving history, these records prove that you completed your court-ordered program.
Frequently Asked Questions
What if I cannot afford the monthly fee?
Contact your provider to ask about hardship waivers or fee reductions. Some states and some providers offer reduced rates for people with low income. If you are denied, you can request a hearing with the court that ordered the device and ask the judge to reduce or waive the fee. Bring proof of your income and expenses.
Can I use someone else's car instead of installing a device in mine?
No. Your court order typically requires the device to be installed in the vehicle you drive most often, or in all vehicles you drive regularly. Driving a vehicle without an interlock device when one is required is a violation and will result in license suspension and possible criminal charges.
What happens if the device malfunctions while I am driving?
Contact your provider when ready and explain what happened. Most providers have emergency protocols for device failure. Driving without a working device is technically a violation, but if you can show the malfunction was not your fault and you reported it right away, the monitoring agency may not count it against you. Keep a record of the date, time, and what happened.
Do I have to test if I have not had anything to drink?
Yes. You must test every time you start the car and every time the device asks for a rolling retest, regardless of whether you have consumed alcohol. The device has no way to know whether you have been drinking except through the breath test. Refusing to test counts as a violation.
Can I drive at night or in bad weather?
Yes. The device works in all conditions — rain, snow, extreme heat, and darkness do not affect it. The only limitation is that you need to be able to blow into the mouthpiece, so if you have a severe respiratory condition or facial injury, talk to your provider about accommodations.