Facing a DUI and hearing the words “ignition interlock”? Here’s the honest truth: for many people, an interlock is what lets them keep working, keep driving their kids and keep their lives moving while they deal with their case. Knowing how it works, and what it costs, takes away a lot of the fear.

This guide explains ignition interlock laws in plain English, what to expect day to day, how to compare providers, and where to find your state’s rules.

What is an ignition interlock device?

An ignition interlock device (IID), sometimes called a car breathalyzer, is installed on your vehicle’s ignition. You give a breath sample before the engine will start. While you drive, it asks for random retests. If it detects alcohol above the programmed limit, the vehicle won’t start and the event is reported to the court or licensing agency monitoring you. Many devices also take a photo at each test.

When is an interlock required?

Every state has an interlock law, but the details differ a lot. More than half of states now require an interlock for every DUI conviction, even a first offense. Other states require it for:

  • Repeat DUI or DWI offenses
  • High blood alcohol content (often 0.15% or above)
  • Refusing a breath or blood test
  • Getting a restricted, hardship or occupational license during a suspension

Your court order or motor vehicle agency letter will say how long you need the device. Terms commonly range from a few months to several years.

Find your state’s interlock rules

What an interlock costs

Most drivers pay an installation fee, a monthly lease and monitoring fee, regular calibration visits and a removal fee. Prices differ by state and company, so compare written quotes. Many states have financial assistance or reduced-cost programs for drivers who qualify, which can make a real difference to a tight family budget.

Comparing interlock companies

Most states certify several providers, such as Intoxalock, LifeSafer, Smart Start, Guardian Interlock, Dräger and Alcohol Detection Systems. Compare:

  • State certification and whether the device is on your state’s approved list
  • Distance to the nearest service center, and whether they offer mobile installation
  • All fees in writing, including lockout and removal fees
  • 24/7 customer support for lockouts or device problems

See certified providers in our sister directory, Ignition Interlock Companies: United States.

Living with an interlock: simple habits that help

  • Rinse your mouth with water and wait about 15 minutes after eating, drinking or using mouthwash before testing.
  • Always complete rolling retests. Pull over safely if you need to.
  • Keep every calibration appointment on your calendar.
  • Never let someone else blow into the device for you.

Each clean test is a small win, and together they show the court and your state that you’re moving in the right direction.

Talk to a DUI attorney first

An experienced DUI attorney can tell you whether an interlock is mandatory in your case, whether the charge can be challenged, and how to get back to driving legally as soon as possible. Also see our guide to DUI car insurance and SR-22 and the full DUI Help Center.

Frequently asked questions

Will I need an ignition interlock after a DUI?

Possibly. More than half of states require an interlock for all DUI offenders, including first-time offenders, and every state uses them in some situations, such as repeat offenses, high BAC or to earn a restricted license. Your court order or motor vehicle agency will say whether it applies to you.

How does an ignition interlock device work?

You blow into the device before starting your vehicle and at random times while driving. If it detects alcohol above the set limit, the engine won't start, and the result is recorded and reported.

Who pays for the interlock?

In most cases the driver pays for installation, monthly monitoring and removal. Many states have reduced-cost programs for drivers who can't afford the full price, so ask your provider and your state.

Can a DUI attorney help me avoid an interlock?

Sometimes. If your attorney gets the charge dismissed or reduced, the interlock requirement may not apply. In other cases, an attorney can help you qualify for a restricted license with an interlock so you can keep driving to work.

Which interlock companies operate in the United States?

Common certified providers include Intoxalock, LifeSafer, Smart Start, Guardian Interlock, Dräger and Alcohol Detection Systems. Each state publishes its own approved list.

What counts as an interlock violation?

Common violations include failed breath tests, skipped rolling retests, missed calibration appointments and tampering with the device. Violations can extend your interlock period or lead to a new suspension.