What is an Ignition Interlock Device (IID) and How does it Work?

What is an Ignition Interlock Device (IID) ?

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What is an ignition interlock device (IID)?

An IID is a small, handheld breathalyzer for car ignitions that’s installed to prevent users from being able to start their vehicle after drinking alcohol. Sometimes they’re referred to as car breathalyzers, or as a breath alcohol ignition interlock device (BAIID). They’re small, about the size of a TV remote.

Most IIDs are made of the following components:

Ignition Interlock Device

Handheld unit

Handheld Unit


Cable Ultimate Guide

Relay Cord

Camera Ultimate Guide

Camera Unit

How do I use an ignition interlock device?

Every device varies, but all require users to submit a breath sample in order to test their Breath Alcohol Content, or BrAC. Intoxalock devices feature a one-button operating system, which helps reduce errors.

To use an Intoxalock IID:

While a failed sample means you won’t be able to start your car, you can be assured the device will NOT be able to turn off your car once it is running. Once your vehicle has been started, no ignition interlock device is able to turn it off. If you fail a random retest, your vehicle will remain on until you remove the keys from the ignition. At this point, your device may lock you out.




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How does an ignition interlock work?

Once the device is installed, drivers blow into the car breathalyzer mouthpiece to provide a breath sample. The device tests for breath alcohol content (BrAC) within the legal limit. If it's under the limit (typically .02), then the driver can put their keys in the ignition and start the car.

Prevent somebody from starting their car while intoxicated

Ignition interlock devices are intended to prevent drivers from starting their vehicle after they’ve been drinking alcohol. Therefore, your car will only start if your breath sample passes.

Each state handles failed breath samples differently. While all states allow you to retest a new breath sample after a waiting period, some have a retest limit. If you hit that limit, you’ll get locked out after multiple failed attempts. Other states allow you to keep submitting samples until one passes.

Continuous sobriety while the vehicle is running

Once your vehicle is started, an ignition interlock device will require you to continue providing breath samples throughout the duration of your trip.

Since Intoxalock’s device is simple, with a one-button design and uncomplicated breath pattern, it’s safe and easy to retest while driving in many situations. Retests prevent drivers from having someone else provide the initial sample, allowing drivers above the limit to start the car.

If your BrAC is above the limit when you re-test, your car breathalyzer will signal you to pull over (if you aren’t already pulled over), and stop your car. The guidelines on retest failure vary by state. Some states will make your horn honk, or lights flash, until you turn off the car. However, the device will NOT be able to turn off your car once it is running. Once your vehicle has been started, no ignition interlock device is able to turn it off.

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How much does an ignition interlock cost?

IIDs are leased, not purchased outright, and the average price is $60-90 a month.

There are many factors that contribute to the overall price of your ignition interlock device, including:

  • The type of vehicle you’re installing your device in
  • The state requiring your installation
  • Any additional features you may be required to have (camera, GPS, wireless reporting)
  • Length of time you are required to have the interlock
  • If you choose, you can enroll in a device protection plan for $10 a month to protect your investment

Ignition interlock cost

Please note that device protection is not available in Georgia or Washington

How long do I need an ignition interlock device?

Each state has its own ignition interlock law that determines when to install the device, how long it will need to be installed, what type of device you need, what monitoring authority will oversee your IID requirement (probation officer, court, DMV, DOT, etc.) and more. Because each state varies, Intoxalock staffs state specialists who know exactly what you need to get your license back.

After you’ve successfully completed your IID requirement, you’ll be allowed to remove the device and reinstate your license. The process for removal varies from state to state, with some requiring you to receive approval from your monitoring authority, some requiring you to call your DOT for an eligibility date or more. Our customer support can help you understand what your state requires to remove the device.

Where do I go for ignition interlock device installation?

Every ignition interlock device needs to be installed by a state-certified provider, and Intoxalock has the most locations with more than 5,000 locations nationwide. Your state specialist will help you find a location near you.

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Where is my nearest location?

Enter your zip code to find the nearest location near you.

More Question

Do you have more questions about Intoxalock devices?

Call us now to speak with a state specialist, or check out our ignition interlock device FAQ.

Customer Help

What resources are there for Intoxalock customers?

Intoxalock offers 24/7 support 365 days a year. You can call anytime to talk to a state specialist about requirements, questions, and anything else related to your Intoxalock IID.