What an interlock device does and why it's installed
An interlock device is a breathalyzer machine wired into your vehicle's ignition system. When your license is suspended due to a DUI or DWI conviction, a court may order you to install one before you can drive legally again. The device prevents your car from starting if it detects alcohol on your breath.
The device does not restore your license. It is a condition that lets you drive during your suspension period, but only after you have met other requirements — usually a conviction, a fine, and sometimes a mandatory waiting period. The interlock requirement typically lasts between six months and three years, depending on your state and the specifics of your case.
You pay for the device yourself. Installation costs between $100 and $300, and monthly monitoring fees run $50 to $100. Some states offer fee waivers for low-income drivers, but you must request this through the court or the device provider.
Key Takeaways
- An interlock device is a breathalyzer wired to your ignition; you must blow into it before the car will start, and it records all attempts.
- The court orders installation as a condition of driving during your suspension, not as a way to get your license back early.
- You choose a certified provider from your state's approved list, schedule installation, and report the device serial number to the court.
- Failing a breath test, tampering with the device, or missing a required service appointment can extend your suspension or result in criminal charges.
- Once your suspension period ends, you must have the device removed by a certified technician and submit proof of removal to the court.
How to find an approved interlock provider in your state
Your state's Department of Motor Vehicles or the court that issued your suspension order will provide a list of certified interlock providers. Call the DMV directly or check their website — do not rely on a provider to tell you they are approved, because unlicensed operators do exist.
Common national providers include Draeger, SmartStart, Guardian Interlock, and LifeSafer, but availability varies by state and county. Once you have the approved list, call three or four providers to compare installation dates and monthly fees. Some charge a flat monthly rate; others charge per service visit. Ask whether the fee includes the initial installation or if that is separate.
Schedule installation as soon as possible after your court order. The device cannot be installed until you have a valid court document stating the requirement — you cannot install it preemptively. Bring your court order, proof of vehicle ownership or registration, and a valid ID to the appointment.
What happens during installation and the first month
Installation takes 30 to 60 minutes. The technician wires the device to your ignition system, steering wheel, and dashboard. You will receive a user manual explaining how to blow into the device (a steady breath for about five seconds), what happens if you fail a test, and the schedule for required service visits.
After installation, you must report the device serial number and provider name to the court within a set timeframe — usually 10 days. Failure to report can be treated as a violation of your court order. The provider will also send a report to the court confirming installation.
The device records every attempt to start your vehicle, every breath test result, and every time you try to tamper with it. The provider downloads this data during monthly service appointments and sends a report to the court. If you miss a service appointment, the provider notifies the court, and your suspension can be extended.
How the device works each time you drive
Before you start the car, you blow into the mouthpiece. The device analyzes your breath for alcohol. If the reading is below your state's threshold (usually 0.02 percent, which is lower than the legal driving limit), the car starts normally. If the reading is above the threshold, the ignition locks and the device records a failed test.
Some states require a "rolling retest" — a second breath test while you are already driving, at a random time. This prevents you from having someone else blow into the device before you drive. If you fail a rolling retest, the device logs the failure and may trigger the horn and lights to alert you to pull over safely.
A single failed test does not automatically extend your suspension, but multiple failures or a pattern of failures can. The court reviews your monthly reports and may order an extension if the data shows repeated violations. Some states allow one or two failures without penalty; others have a zero-tolerance policy.
What counts as tampering and what the penalties are
Tampering includes disconnecting the device, using a bypass tube, asking someone else to blow into it, or attempting to start the car without blowing into the device. The device records all of these actions and reports them to the court. Tampering is a separate criminal offense in most states and can result in jail time, additional fines, or an extended suspension.
Missing a required service appointment is also treated as a violation. The provider will attempt to contact you; if you do not reschedule within a set window (usually 7 to 14 days), they report the missed appointment to the court. This can trigger an extension of your suspension or a warrant for your arrest.
Driving a vehicle without the device during your suspension period is a separate crime. If you are stopped and the officer discovers you are driving an unequipped vehicle, you face additional charges on top of your original DUI conviction.
Removing the device when your suspension ends
Your suspension period is set by the court at sentencing. When that period ends, you do not automatically regain your license — you must have the device removed by a certified technician from your provider. Schedule the removal appointment and bring your court order or a letter from the court stating that your suspension has ended.
The technician will remove the device, inspect your vehicle for damage, and provide you with a removal certificate. You must submit this certificate to the court or DMV within a set timeframe (usually 10 days) to complete the process. Some states require you to pass a written test or pay a reinstatement fee before your license is fully restored.
Keep the removal certificate and any court correspondence in a safe place. If you are pulled over after your suspension ends and the officer questions whether your license is valid, you will need proof that the device was removed on time.
Costs and financial information options
The total cost of an interlock device over a typical 12-month requirement ranges from $1,200 to $2,400, including installation, monthly monitoring, and service visits. This does not include the original DUI fine, court costs, or increased insurance premiums.
Some states and counties offer fee reductions or waivers for drivers below a certain income threshold. Contact your local court's probation department or the interlock provider to ask about hardship waivers. You will need to provide proof of income, such as recent pay stubs or tax returns.
A few states allow you to request a payment plan from the provider, spreading the cost over several months. Ask about this option when you call for installation quotes. Some providers also offer discounts if you pay the full year upfront rather than monthly.
Frequently Asked Questions
Can I drive someone else's car instead of using my own vehicle?
No. Your suspension order applies to you as a driver, not to a specific vehicle. If you are caught driving any vehicle without an interlock device during your suspension, you face additional criminal charges. The device must be installed in any vehicle you operate regularly.
What if I fail a breath test because I used mouthwash or ate something with alcohol?
The device is designed to distinguish between mouth alcohol (which clears quickly) and breath alcohol from your bloodstream. If you fail when ready after using mouthwash, wait 15 minutes and request a retest. If you fail a retest, the device records it as a violation. Keep receipts or documentation of what you consumed if you believe a failure was caused by food or hygiene products.
Do I have to keep the device if I sell my car?
Yes. If you sell your vehicle, you must have the device transferred to a new vehicle or removed and reinstalled in a replacement car. You cannot straightforward remove it and stop driving. Contact your provider when ready to arrange a transfer. Your suspension period does not end until the court says it does.
What happens if I move to a different state?
Contact your original state's court and the new state's DMV before you move. Some states honor interlock requirements from other states; others do not. You may need to have the device transferred to a provider in your new state, or your suspension may be extended. Do not move without resolving this with both states.
Can I remove the device myself to save money?
No. Only a certified technician can remove the device, and you must submit proof of removal to the court. Removing it yourself is tampering and is a criminal offense. The court will know if the device is missing because the provider will report it.