What Is an Ignition Interlock Device and When Is It Required in Maryland?

 Posted on April 09, 2026 in DUI / DWI

An ignition interlock device (IID) is a breathalyzer connected to your car's ignition that prevents the vehicle from starting if alcohol is detected on your breath. In Maryland, the rules around who must use one have become significantly stricter in recent years. Under Maryland Transportation Code § 16-404.1, the requirement was expanded to cover more first-time DUI offenders and those with lower blood alcohol levels. If you are facing a DUI charge in 2026 and are worried about what this means for your license and your life, the Harford County, MD DUI defense lawyer at Baltimore Legal Services can help.

How Does an Ignition Interlock Device Work?

If an IID is installed in your car, you must blow into it before you can start the engine. If your breath alcohol level is above a preset limit, the car will not start. In Maryland, that limit is set at 0.025 percent, which is well below the legal limit for driving.

The device does not just test you at startup. It also requires random retests while you are driving. If you fail a retest or miss one, the device logs the event and reports it to the program administrators. The data is reviewed regularly to make sure you are following the rules.

IIDs must be installed by a provider approved by the Maryland Motor Vehicle Administration. You are responsible for the cost of installation, maintenance, and monthly monitoring fees.

Who Is Required To Have an Ignition Interlock Device in Maryland?

Under the updated Maryland law, the ignition interlock requirement now applies to a broader group of drivers than it did before. Those currently required to participate include:

• Anyone convicted of DUI with a blood alcohol concentration (BAC) of 0.08 percent or higher
• Anyone convicted of DWI with a BAC between 0.07 and 0.0799
• Anyone who receives a probation before judgment for an alcohol-related DUI offense
• Anyone who refused to take a breath or blood test at the time of their arrest
• Anyone convicted of DUI with a minor in the vehicle
• Repeat DUI or DWI offenders, regardless of BAC level

The recent changes to the law closed the loophole that had previously allowed people who received probation before judgment to skip the interlock requirement. That exemption is gone. If you receive a PBJ for DUI now, you still have to install the device.

How Long Do You Have to Use an Ignition Interlock Device in Maryland?

The length of time you must use the device depends on the specifics of your case. Maryland law sets minimum participation periods based on the offense and your history:

• For a first-time DUI offense with a BAC between 0.08 and 0.14, the minimum enrollment period is 180 days.
• If your BAC was 0.15 or higher, the minimum is one year.
• If you refused a breath test, the minimum is one year.
• For a second offense, the minimum is one year.
• For a third or subsequent offense, the minimum is three years.

The court or the MVA may require a longer period depending on the circumstances of your case. Time you already spent on the interlock before your court date may count toward your required period, but only if the MVA grants you that credit.

Can the Ignition Interlock Requirement Be Challenged or Reduced in Maryland?

The interlock requirement itself is tied to the outcome of your DUI case. This means one of the best ways to limit or avoid the interlock requirement is to fight the underlying charge. If the charge is reduced, dismissed, or handled in a way that does not trigger the mandatory interlock provisions, the requirement may not apply or may be shorter.

A DUI defense attorney can look at the evidence against you, challenge the validity of the breath test, examine whether the traffic stop was lawful, and explore every option available to make the circumstances work as well for you as possible.

Schedule a Free Consultation With Our Northern Baltimore County, MD DUI Defense Attorney

At Baltimore Legal Services, our attorney has helped more than 10,000 clients navigate the legal system. We offer custom flat fees so you always know exactly what your legal representation will cost, with no surprises. With more than 15 years of experience handling DUI cases in Maryland, Attorney Brendan O'Brien knows how to build a defense that gives you the best possible chance at protecting your license and your future.

Call 858-523-8423 today to speak with a Harford County, MD DUI defense lawyer you can trust. We are available 24/7.