How an Ignition Interlock Device Works

InterlockInstall - March 27, 2021

Also known as breathalyzers, ignition interlock devices (IIDs) are installed in the vehicles of individuals charged with DUI to minimize additional drunk driving offenses. The courts and the Department of Motor Vehicles (DMV) have implemented ignition interlock device installation […] as a way to prevent impaired driving.

How Ignition Interlock Devices Work

Ignition interlock devices will require the driver to blow into the device to start the car. Drivers will also be required to periodically blow into the device while it is in motion. If the breathalyzer detects alcohol on the driver's breath, the vehicle will not start (when already in motion, it will shut down gradually).

The IID analyzes the blood alcohol concentration (BAC) of the breath sample provided. If the BAC is beyond the preset limit, the fuel cell found inside the device triggers a relay that will open so the car won't start. When the vehicle is in motion, "rolling retests" will be required.

The rolling retests are designed to ensure intoxicated drivers won't have a sober person blow into the car to start it. Most IIDs also come equipped with a recorder. The recorder will register positive BAC readings or any failed attempts to start the vehicle. IIDs are designed to only measure the BAC so they can't measure or detect drugs.

About the Author
Lauren McDowell is the Content Marketing Strategist for Interlock Install [], a Phoenix-based company that performs the installations, service appointments, and removals for ADS Interlock. When not writing, she attends book clubs and enjoys reading stories to her kids.