What an Ignition Interlock Device Does

An ignition interlock device is a breathalyzer installed in your vehicle that prevents the engine from starting if it detects alcohol on your breath. The device measures your blood alcohol content (BAC) through a breath sample you provide before the car will turn on. If your BAC is above the legal threshold set by your state — typically 0.02 percent for drivers with an interlock requirement — the vehicle will not start.

The device also requires periodic breath samples while you are driving, called rolling retests. If you fail a rolling retest, the vehicle will not shut off when ready, but the interlock will log the failure and may trigger a horn or light to alert you. The device records all test results and violations, and those records are reported to the court or monitoring authority overseeing your case.

Ignition interlocks are not optional devices you choose to install. They are court-ordered requirements, usually imposed after a DUI or DWI conviction, or sometimes as a condition of license reinstatement. The length of time you must use one depends on your state's laws, the severity of your offense, and whether you have prior convictions.

Key Takeaways

  • An ignition interlock requires a breath sample before your car will start, and the device logs all results for court review.
  • Most states require interlocks for a minimum of 6 to 12 months, though repeat offenders may face longer periods.
  • You pay for installation, monthly monitoring, and removal, with total costs typically ranging from $1,000 to $3,000 over the required period.
  • Tampering with, bypassing, or failing repeated breath tests can result in license suspension, fines, and additional criminal charges.
  • Some states offer hardship waivers that allow you to drive to work or medical appointments without an interlock, though the requirements are strict.

How Long You Must Use an Ignition Interlock

The mandatory period varies significantly by state and by your specific case. Most states require a minimum of 6 months for a first offense, though some require 12 months or longer. If you have prior DUI convictions, the period typically extends to 1 to 3 years. A few states, including Arizona and New Mexico, impose longer mandatory periods as a matter of law.

The court order will specify your exact start and end dates. You cannot remove the device early unless you petition the court and demonstrate that you have complied with all requirements — passing all breath tests, paying all fees, and maintaining a clean driving record during the interlock period. Some judges will grant early removal; others will not, regardless of your compliance record.

If you fail a breath test or tamper with the device, the court can extend your interlock requirement by months or even years. A single violation does not automatically trigger an extension, but a pattern of failures or attempts to bypass the device will result in court action.

Installation, Monitoring, and Removal Costs

You are responsible for paying all costs associated with the interlock device. Installation typically costs between $100 and $300, depending on the service provider and your vehicle. Monthly monitoring fees range from $50 to $100 per month, though some providers charge less in states with price regulation.

Removal of the device at the end of your required period costs between $50 and $150. If you are required to use the interlock for 12 months at $75 per month, your total cost would be approximately $1,000 to $1,200 before installation and removal. Over a 2-year period, costs can easily exceed $2,000 to $3,000.

Some states cap the monthly fee that providers can charge, while others do not. A few states have programs that reduce or waive fees for low-income drivers, though these programs are limited and vary widely. Contact your state's Department of Motor Vehicles or the court that ordered your interlock to ask whether fee reduction is available in your situation.

What Happens If You Fail a Breath Test

A failed breath test is recorded by the device and reported to the monitoring authority. A single failure does not automatically result in criminal charges or license suspension, but it does create a record that the court can review. If you have only one or two failures over your entire interlock period and they are explained by circumstances like mouthwash or medication, the court may take no action.

A pattern of failures — typically three or more within a set period, often 30 days — can trigger a violation report to the court. The court may then schedule a hearing to determine whether to extend your interlock requirement, suspend your license, or impose additional penalties. Some states have mandatory extension rules: if you fail more than a certain number of tests, your interlock period is automatically extended by a set amount, usually 6 months to 1 year.

Repeated failures also suggest that you may not be complying with the spirit of the interlock requirement, which is to prevent you from driving under the influence. The court views this as a serious matter, and the consequences can include loss of driving privileges, fines, or even jail time in extreme cases.

Tampering, Bypassing, and Other Violations

Attempting to tamper with, bypass, or disable an ignition interlock device is a separate criminal offense in all states. Common violations include asking someone else to blow into the device for you, disconnecting the device, or using a device designed to defeat the interlock. These actions are felonies in some states and misdemeanors in others, and they carry penalties including fines, jail time, and permanent license revocation.

Modern interlock devices have anti-tampering features that detect disconnection, power loss, or attempts to introduce foreign substances. If the device detects tampering, it locks and sends an alert to the monitoring authority. You will be required to have the device serviced, and the tampering will be reported to the court.

Even if you believe the interlock is malfunctioning or giving false readings, you cannot remove it yourself. If you suspect a malfunction, contact the service provider or the court and request an inspection. Removing the device without authorization is a violation regardless of whether the device was working correctly.

Hardship Waivers and Restricted Driving Permits

Some states allow you to petition for a hardship waiver or restricted driving permit that lets you drive to work, school, medical appointments, or court-ordered treatment without an interlock installed. The requirements for a hardship waiver are strict and vary by state. You typically must demonstrate that you have no reasonable alternative transportation, that the interlock would cause undue hardship, and that you have complied with all other court orders.

A hardship waiver does not eliminate the interlock requirement; it suspends it for specific trips. You must still have the device installed and must use it for all other driving. Some states require you to install a monitoring device in your vehicle instead, which tracks your location and driving patterns without requiring a breath test.

To request a hardship waiver, you must file a petition with the court that ordered your interlock. You will need to provide documentation of your employment, school enrollment, medical treatment, or other necessity, and you may need to attend a hearing. The court has discretion to grant or deny the waiver, and approval is not may provide even if you meet the stated criteria.

State Variations in Interlock Laws

Interlock requirements differ significantly across states. Some states impose interlocks only for repeat offenders or high BAC readings, while others require them for all DUI convictions. A few states, including Arizona, require interlocks for first-time offenders with BAC above 0.15 percent. Others, like California, allow judges discretion in whether to order an interlock.

The length of the mandatory period also varies. New York requires a minimum of 6 months for a first offense; Arizona requires 12 months. Some states allow early removal after a set period if you have a clean record; others do not. A few states have "ignition interlock-only" license suspension options, which allow you to drive with an interlock but not without one.

If you are moving to another state while under an interlock requirement, you must comply with both your home state's requirement and your new state's laws. Some states will recognize an interlock requirement from another state; others will not. Contact the Department of Motor Vehicles in both states before you move to understand your obligations.

Frequently Asked Questions

Can I remove the interlock device myself if I think it is broken?

No. Removing the device yourself is a criminal violation, even if you believe it is malfunctioning. Contact the service provider or the court and request an inspection. If the device is defective, the provider will repair or replace it at no cost to you.

What if someone else needs to drive my car while I have an interlock?

They can drive your car, but the interlock will still require a breath sample before the engine starts. If they have consumed alcohol, the car will not start. Some people with interlocks have a second vehicle without an interlock for other drivers to use, though this is not required by law.

Does the interlock show up on my driving record or criminal record?

The interlock requirement itself appears on your driving record and is visible to insurance companies and law enforcement. Violations of the interlock requirement — failed tests or tampering — may be reported to the court and could affect your case, but they do not automatically create a separate criminal record unless you are charged with a new offense.

Can I get the interlock requirement waived or shortened?

Only the court that ordered the interlock can waive or shorten the requirement. You can petition the court with evidence of compliance and hardship, but approval is not may provide. Some judges are more willing to grant early removal than others, and it depends on the facts of your case and your state's laws.

What happens if I move out of state before my interlock period ends?

You must comply with your home state's requirement even if you move. Some states will recognize an interlock requirement from another state; others will not. Contact both states' Departments of Motor Vehicles before you move to understand whether you can transfer your requirement or whether you must return to complete it.