How Does an Ignition Interlock Device Work?

Ignition Interlock Device (IID) Facts

If you were convicted of a DUI, you may not only suffer fines, jail time and a license suspension but also an ignition interlock device (IID). An IID is similar to a mobile breathalyzer; it’s a small handheld mouthpiece installed in your vehicle to measure your BAC. The purpose of an IID is to prevent you from drinking and driving.

How Does an Ignition Interlock Device WorkOnce you’re notified that you must install an IID in your vehicle due to your DUI conviction, it’s important to find an authorized West Virginia IID provider. Make an appointment to get your IID installed, and bring identifiable documents including your driver’s license, vehicle registration and court order. Once it’s installed, you must prepare to change your habits for the duration of your installation period.

Every time you get in the car, you must pass a breath test or else your vehicle won’t start. Turn your key or press “start” to turn your vehicle on, blow into the mouthpiece and if your BAC is less than the legal limit, you can start your vehicle and drive. If it is above the legal limit, your car won’t start. Some IIDs have a camera component that verifies your identity and confirms that the breath test sample is yours, and not someone else’s.

It’s worth noting that you may be required to submit to a rolling retest while your vehicle is running. These tests are completely random and occur while you’re driving. When your IID notifies you that it’s time to take a rolling retest, safely pull over and take the breath test. If your BAC is below the legal limit, you can continue driving. If it’s not, your vehicle’s engine will not stop running, but your lights and horn may activate. In this case, turn off the ignition and wait until you’re required to blow into the device again.

Questions? Harley Can Help.

An IID takes some time to get used to. You have probably driven your car for years and decades, so handling an IID can be a rude awakening and force you to acclimate to new driving habits as a result. The Wagner Law Firm is here to help guide you through the IID process and provide the legal counsel you need to best avoid deeper trouble. IID technology isn’t perfect, so it’s important to learn how to navigate these devices and use them successfully.

To learn more, please contact us online or call (304) 461-6000 today!

Harley Wagner Avatar

Harley Wagner

Attorney Thomas M. Cooley School of Law, National College for DUI Defense, West Virginia State Bar

Harley has represented over 3,000 citizens throughout West Virginia. He is the author of West Virginia DUI Defense, The Law and Practice, which is the go to handbook for many magistrates, judges, defense attorneys, prosecutors, and law enforcement throughout West Virginia. has been selected for inclusion in West Virginia Super Lawyers® eight times.

He maintains an AV Preeminent® Rating by with Martindale-Hubbell®, an Avvo Rating of 10.0, and an excellent annual rating from the Better Business Bureau.

Harley is also the past president of the national DUI Defense Lawyers Association (2020-2021) which he was Charter Member and founder of in 2014

Areas of Expertise: DUI Defense, Aggravated DUI, Alternative Sentencing, Boating Under the Influence, Commercial License DUI, DMV Hearings, DUI Drugs, DUI with Injury, DUI Causing Death, Out-of-State Resident DUI, DUI Immigration Consequences, DUI with Minor in Vehicle, DUI Child Endangerment, Fleeing a DUI, Felony DUI, Permitting DUI, Underage DUI, Multiple DUI, First-Offense DUI, Second-Offense DUI, Third-Offense DUI, DUI Testing, Field Sobriety Tests, Breathalyzer, Blood Testing, DUI Info Center, College Student DUI, DUI Checkpoints, DUI Court Dates, DUI Deferral Program, Implied Consent, Test & Lock Program, FAQ, DUI Penalties, Administrative License Revocation, Ignition Interlock Device, License Suspension