Ignition Interlock Device: Purpose And Functionality Explained

Driving is a privilege that comes with great responsibility. Every time we get behind the wheel, we must ensure that we are sober, alert, and attentive to the traffic rules and the road conditions. One way to ensure that drivers are fit to operate a vehicle is to use an Ignition Interlock Device (IID).

By requiring drivers to pass a breath test before starting their car, ignition interlock devices can reduce the risk of drunk driving and its devastating consequences. So, let’s dive in and explore the remarkable potential of ignition interlock devices in fostering safe and responsible driving.

What is an Ignition Interlock Device?

An IID is a breathalyzer installed in a car’s ignition system. It inhibits engine ignition when the driver’s blood alcohol concentration (BAC) surpasses a predetermined threshold. Courts or licensing authorities often mandate ignition interlock installations for drivers convicted of driving under the influence (DUI) or other alcohol-related offenses.

Ignition interlock devices comprise three primary parts: a breathalyzer unit, a control module, and wiring with connectors. The breathalyzer unit is positioned on the dashboard or near the steering wheel, with a mouthpiece for the driver to blow into. The control module is installed in a concealed location. The wiring and connectors connect the breathalyzer unit and the control module.

How Ignition Interlock Devices Function

IIDs play a crucial role in preventing alcohol-impaired driving in a straightforward process. It starts with drivers providing an initial breath sample, which is carefully analyzed for alcohol content. If the result falls below the predetermined limit, the ignition is enabled, allowing the driver to start the vehicle.

Rolling retests are conducted at random intervals to ensure continued sobriety throughout the journey, serving as additional checks to confirm that the driver remains alcohol-free. Failing a rolling retest or missing it triggers an event logging and may activate warning signals like honking or flashing lights.

IID Calibration and Accuracy

Calibration ensures that the breath alcohol concentration readings remain reliable. Certified technicians calibrate the devices at specified intervals, typically every 30 to 60 days. It involves adjusting and verifying the device’s sensors and analyzing data output to maintain high accuracy in detecting alcohol levels.

Benefits of Ignition Interlock Devices

Ignition interlock devices hinder vehicle ignition in the presence of a driver with a blood alcohol concentration exceeding a specified limit. IIDs also have several benefits, including:

Reducing impaired driving incidents

IIDs can deter drivers from drinking and driving, as they know they cannot start their vehicle if they do so. It can reduce the number of impaired driving incidents and crashes, which can save lives and prevent injuries.

Lowering DUI recidivism rates

IIDs can additionally assist individuals with DUI convictions in preventing the recurrence of such offenses. Studies have shown that IIDs can reduce DUI recidivism rates by 50% to 90%, compared to other sanctions such as license suspension or fines.

Positive impact on personal behavior and decision-making

IIDs can also positively impact the personal behavior and decision-making of drivers who use them. IIDs can help drivers develop more responsible drinking habits, as they have to monitor their BAC and plan to drive. IIDs can also motivate drivers to seek treatment or counseling for alcohol abuse or addiction if needed.

Encouraging responsible alcohol consumption

IIDs can also encourage responsible alcohol consumption among the general public, as they raise awareness of the dangers and consequences of impaired driving. IIDs can also create a social norm of not drinking and driving, as drivers who use them can influence their peers and family members to do the same.

Installation and Usage of Ignition Interlock Devices

Ignition interlock installation is subject to certain eligibility criteria, which vary depending on jurisdiction and the nature of the offense. People guilty of DUI or DWI offenses might need to install an IID. Some jurisdictions may also mandate IIDs for first-time offenders with high blood alcohol concentrations or those involved in accidents resulting in injuries.

Here are the steps involved in an IID installation:

  1. The individual must locate an authorized IID service provider approved by the relevant authorities.
  2. An appointment is then scheduled for the installation.
  3. During the installation, a trained technician will connect the device to the vehicle’s ignition system and install a mouthpiece or a handset for breath sample collection.
  4. Finally, the technician will explain the device’s operation and provide instructions for proper usage.

IID Maintenance and Servicing Requirements

Service providers typically schedule periodic appointments for calibration and device inspections. During calibration, the device’s accuracy is verified and adjusted if necessary. Additionally, drivers must promptly report any issues or malfunctions to the service provider, who will address the problem and provide necessary repairs or replacements.

Costs Associated With IID Installation and Usage

The costs of installation and usage of an IID may vary depending on several factors, such as:

  • Type and features of the device
  • Provider and location
  • Duration and conditions of the program
  • State laws and regulations
  • Driver’s income level and eligibility for financial assistance

The average costs of installation and usage of an IID are as follows:

  • Installation fee: $100-$200
  • Monthly monitoring fee: $50-$100
  • Calibration fee: $20-$50 per visit
  • Removal fee: $50-$100
  • Additional fees: $10-$50 for battery replacement, filter replacement, data download/printout etc.

Some states may offer financial assistance or reduced fees for low-income drivers who qualify for their programs. Drivers should contact their state’s DMV, court, or probation officer for more information on available options and requirements.

Ignition Interlock Legal Implications and Regulations

IIDs must adhere to laws and regulations for installation and use to promote road safety and prevent drunk driving. They vary by jurisdiction and cover eligibility, installation, maintenance, and consequences for non-compliance.

Jurisdictions and states where IIDs are mandatory

Many jurisdictions and states have made IIDs mandatory for certain DUI or DWI offenses. The exact requirements can vary, but they often apply to repeat offenders or individuals with high blood alcohol concentrations.

Some states have expanded the mandatory IID installation to include first-time offenders as a preventive measure. It is important to consult local authorities or legal professionals to understand the specific requirements in a particular jurisdiction.

Penalties for tampering or circumventing an IID

Intentionally bypassing or manipulating the device undermines its purpose and compromises road safety. Penalties for tampering with an IID can include fines, extended IID installation periods, license suspensions, or even imprisonment, depending on the offense’s jurisdiction and nature.

Expungement and removal of IIDs

Expungement refers to removing a conviction from an individual’s record, while removal involves uninstalling the IID from the vehicle.

In certain jurisdictions, individuals who have completed the mandatory installation period and fulfilled all legal obligations may be eligible for the expungement or removal of an ignition interlock device. To navigate this process effectively, seeking guidance from a qualified legal professional is highly recommended.

ADAS Calibration

When installing IIDs, ADAS calibration is vital. Skilled technicians specialize in precision calibration, ensuring seamless operation of IIDs and ADAS features like lane departure warnings and adaptive cruise control.


Ignition interlock devices (IIDs) are effective tools to prevent drunk driving and reduce traffic fatalities. They also help drivers with alcohol problems to rehabilitate and avoid legal consequences.

It is important to recognize that while IIDs are valuable safeguards, they should not be viewed as a substitute for personal responsibility and awareness. Drivers must always prioritize adherence to the law and make responsible choices, refraining from drinking and driving, regardless of whether an IID is installed in their vehicle.

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.