How Does an Ignition Interlock Device Work?

An Ignition Interlock Device works by requiring a driver to blow into a mouthpiece to test their Breath Alcohol Concentration (BrAC) before they can start a vehicle. If the device detects a BrAC greater than a level determined by the monitoring authority, it prevents the engine from being started.

Ignition Interlock is typically a requirement or an option in any DUI offense, depending largely on guidelines set by the state or local jurisdiction. Every state has some sort of Ignition Interlock law, though their application varies widely.

It’s relatively easy to understand how Ignition Interlock works, but you may have additional questions. Fortunately, as the world leader in Ignition Interlock technology, Smart Start is your one-stop source for information. Whether you’re just getting started with Ignition Interlock or are finishing your program, we’re here to help.

Ignition Interlock doesn’t have to be complicated

An Overview: How an Ignition Interlock Device Works

During more than 25 years as the Ignition Interlock leader, Smart Start has created a device that’s sleek and compact – not much bigger than a smartphone. Smart Start technicians make it a priority to install the device in a convenient, discreet place near the driver’s seat that doesn’t attract attention from passengers.

When you attempt to start your car, the Ignition Interlock Device will interrupt the signal from the ignition to the starter unless a valid breath sample is provided. You’ll blow into the mouthpiece; if the sample is within the appropriate guidelines, the car will start.

There’s no magic involved in determining the BrAC. Our Ignition Interlock Devices work by using sophisticated fuel cell technology to measure BrAC.

What’s the difference between BrAC and Blood Alcohol Content?

Remember the Random Retest

You may also be prompted to perform what is typically called a “rolling retest,” which is intended to prevent any drinking after the initial test. We actually prefer the term “random retest,” since you should never perform the test while the car is moving. Always pull safely off the road before a random retest.

These tests are set at random intervals. You won’t know in advance when they will occur.

It’s important to remember:

  • A random retest will always allow you time to safely pull your vehicle over, perform the test, and continue on your way.
  • If you fail a random retest, your engine will never suddenly stop. However, the Ignition Interlock Device will log the positive test result.
  • If a breath sample isn’t provided, or is outside of the programmed limits of the device, the device will log the event and warn you about the violation.

Why are random retests necessary?

Calibrate the Device on a Regular Basis

In order for an Ignition Interlock Device to work correctly, it must be calibrated on a regular basis. Most jurisdictions require calibration every 30 to 60 days; Smart Start recommends a 30-day interval.

When you visit a Smart Start location, a technician will:

  • Check your device and your system to make sure everything is working properly.
  • Perform any necessary programming updates for the device.
  • Download any test data and forward it to your monitoring authority.

Calibration usually takes around 15 to 20 minutes, and can be performed at any of more than 1,800 Smart Start locations. The device will alert you when it needs service. If you miss a service appointment, you may be prevented from starting your vehicle.

At that point, you may be required to have your car towed to a Smart Start service center to be unlocked. Depending on your jurisdiction, you may be provided with a temporary unlock code that will allow you to drive your car to the service location.

How does temporary unlock work?

It Takes Time to Learn How Ignition Interlock Works

That’s a high-level overview of how Ignition Interlock works. It’s not complicated, but there are a lot of details to keep in mind.

Your Smart Start Ignition Interlock Device is designed to be simple to use, and easy to take care of. Still, it’s virtually impossible to know everything about your device. That’s especially true when you’re just beginning your interlock program, or if you’re unsure about rules or regulations that are specific to your area.

That’s why it’s priceless to have the best customer care, available 24/7/365, from Smart Start’s knowledgeable professionals. If you’ve got questions, we’ve got answers.

If you need to learn more about Ignition Interlock or make an installation appointment, call Smart Start at (800) 831-3299. It’s easy to find a service center near you.