How Does An Ignition Interlock Device Work?

If you’ve been convicted of DUI, depending on what state you live in, you may be required to get an ignition interlock device (IID) installed in your vehicle(s) as part of regaining full driving privileges. The length of time you have the device installed will depend on your state’s laws and how well you comply with the rules of the program. All 50 states have ignition interlock laws, and there are a number of so-called all offender states, where IIDs are required for all offenses, even first-time DUIs. So, you may be asking yourself, How does an ignition interlock device work?

Let’s explain. Whether you get your ignition interlock device from ALCOLOCK or some other company, they work pretty much the same. Essentially, the IID is an in-car breathalyzer that hooks into your car’s ignition/starter system. The IID is composed of two parts — the handheld device with a mouthpiece that you blow into, and the Electronic Control Unit (ECU) which is physically connected to the starter.

The handheld device senses alcohol on your breath, or the lack of alcohol. Each time you blow into the device, it communicates your breath alcohol content (BAC) to the ECU. If the device doesn’t detect any alcohol, you are able to start the car as you normally would. If the device detects even the smallest amount of alcohol on your breath, the ECU prevents you from starting the car.

Ignition Interlock Devices Are Sensitive and Highly Accurate

Ignition interlock devices today use an ethanol fuel cell sensor to provide the precision and accuracy required by the National Highway Transportation Safety Administration’s (NHTSA) model specifications for breath alcohol IIDs. Here’s where we get a bit technical. Fuel cell sensors use an electrochemical process where any amount of alcohol on your breath reacts with a catalytic electrode. That reaction produces an electric current. The IID measures that current to determine your BAC. The more alcohol on your breath, the higher the BAC level.

Most states have the level set at .02 or .025 BAC as the level at which you are locked out. To put it into perspective, for most people, one drink is all it takes to blow a .02.That’s because alcohol immediately enters your bloodstream, and your bloodstream carries that alcohol to every part of your body, including your lungs.

How Often You Have to Give a Breath Sample

You have to blow into the ignition interlock device each time you want to start the car. Then, the IID will require random breath samples as you are driving. These are called rolling retests. The device will give you an audible alert and put a message on the screen for several minutes in advance of when you need to give the breath sample.

If you pass the rolling retest, you keep driving. If you fail the rolling retest, the device WILL NOT SHUT DOWN YOUR VEHICLE. That would be a major safety issue. But the device will record the test failure.

What Information the Ignition Interlock Device Records

The ignition interlock device records a huge amount of information, including:

  • Date, time, and results each time you take the start-up test
  • Date, time, and results each time you take a rolling retest
  • Your location if the device is GPS equipped
  • Your picture each time you take a test if the device is camera-equipped
  • If you skip a rolling retest
  • If you attempt to tamper with or remove the device
  • And more, depending on your state requirements

In most cases, your state will require you to bring your vehicle into one of our service centers every 30 days so we can re-calibrate the device if needed, and download all of the information the device has recorded. We then make that information available to your monitoring agency, which can be the court system, your probation officer, the DMV, etc.

What Happens if You Fail the Breath Test

Each state has different requirements, but if you fail the test a certain number of times in a row, you may be locked out for up to 24 hours. At the time of your interlock device installation, your technician will go over how to use the device, and what your program requirements are.

If you fail the breath test a certain number of times, your state may extend the amount of time you have to have the IID installed in your vehicle. They can also kick you out of the program altogether and reinstate your full license suspension period.

To get your full driving privileges back as soon as possible, it pays to comply with all of the program regulations. If you’ve been drinking, ride home with a sober driver or call an Uber. Ask to sleepover at a friend’s house. Whatever it takes to avoid additional penalties.

Schedule Ignition Interlock Device Installation

If you or a loved one has been convicted of DUI and you need to get an IID installed on your vehicle, help is just a phone call away. Call one of our service locations directly, or call ALCOLOCK at (866) 700-9300. Be sure you have all of the paperwork from the courts and the Department of Motor Vehicles when you call. If this is a voluntary installation, you don’t need any paperwork from the courts or the state. We will ask you a few questions and share some information before getting you on the schedule. We offer fast and affordable ignition interlock device installation and maintenance.

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