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How to Use an Ignition Interlock Device

An ignition interlock device is a big change. Once your device is installed, you will be unable to start your vehicle without taking and passing a breath alcohol content (BrAC) test. The way you test and operate the ignition interlock device or car breathalyzer does vary depending on which interlock provider you choose, but the testing requirements will be similar as these are mandated by the state. 

Starting and stopping your car with an IID

Ignition interlock devices are wired into your vehicle’s ignition, and you must provide a passing breath sample before you can start your car. Failed tests will be reported to the state monitoring authority, and could result in further penalties or an increased interlock term. 

Your interlock provider should share specifics for testing at installation, and most provide online resources as well. Our chosen provider, Intoxalock, has many videos about how to use their devices. 

To test:

  1. Make sure your device is on and ready for testing
  2. Follow the breath method prescribed by your provider (Intoxalock uses a blow-inhale-blow method, other providers have different patterns like blow-hum-blow)
  3. When your sample is analyzed, your IID unit should display the result
  4. When you have passed the test, you will have a period of two to three minutes to start the vehicle

If you fail the test, you will be able to try again, but will not be able to start the car until you pass. In many states, repeated failures could result in a device lockout. A device lockout will require you to contact your service provider before you can proceed. When your device is in lockout mode, you will be unable to start your car at all.

During your trip, your device may request random retests. An alarm will sound, and you will have a grace period to pull over for testing if you need to.

When you arrive at your final destination, check your device to be sure there are no random retest requests. Even though you are stopping your vehicle, missing a retest request could cause a lockout. If there are no requests, it is safe to stop your vehicle. 


Everything you need to know about random retests

Random retests are performed to ensure continuous sobriety and prevent tampering. Every state requires random retests for court-mandated interlock users (some states do not require random retests for voluntary interlock users). 

The typical time period for most states is once per hour, but the time between tests varies depending on the state law. 

Your interlock device will alert you by beeping or sounding an alarm to indicate a test is required. Most providers provide a grace period. Our chosen provider, Intoxalock, allows drivers six minutes if they need to pull over. If you’re comfortable testing while driving, most devices can be operated while driving, but the option to pull over is there for anyone who needs to.

Skipping a random retest might result in:

  • Vehicle's horn may start honking
  • Lights might begin flashing
  • An internal alarm might go off
  • The device could lock you out once you stop driving

Please note: An interlock device will NEVER cause your car to stop while in motion, even if you miss or fail a random retest. 


If you have any questions about interlock testing, random retests, providing samples, or anything interlock related, we can help. Contact us at 877-370-7308 to discuss all things interlock.