An interlock device is a breath-testing unit connected to a vehicle’s ignition system. Drivers required to use one provide a breath sample before starting the car and may need to test again while driving. If you are researching what is an interlock device, this guide explains the equipment, the routine, and the questions to confirm before arranging service.
Ask about installation and service
What does an interlock device do?
An ignition interlock device (IID) is sometimes called a car breathalyzer. It measures alcohol in a breath sample and is wired into the vehicle so the engine will not start unless the sample meets the programmed requirements. It is not a substitute for a driver’s judgment, and it does not make it safe to drive after drinking.
An IID generally has two parts: a handheld unit used to provide a breath sample and a vehicle connection installed by a technician. The specific device and program rules determine how the device operates, what data it records, and how often it must be serviced. A device is assigned as part of a legal or administrative requirement; it is not simply a consumer accessory to use at will.
The National Highway Traffic Safety Administration describes ignition interlock devices as breath alcohol ignition interlock devices in its research literature; one peer-reviewed study examined potential injury-prevention effects of interlock installation. That research concerns population-level modeling, not a promise about an individual driver’s outcome. Read the study, Modeling the Injury Prevention Impact of Mandatory Alcohol Interlock Installation, for its scope and methods.
What does an interlock device look like?
The handheld component is usually a small unit attached by a cord, positioned so the driver can reach it from the driver’s seat. It has a mouthpiece or sample port and a display or indicators that guide the test. The vehicle wiring and control module are generally installed out of the way. Exact appearance varies by model, so drivers should learn their own unit during installation.
The device is separate from a phone app or a portable standalone breathalyzer. Some standalone breathalyzers can help a person check a sample, but they do not control a car’s ignition and do not replace a required IID. For a basic overview of terminology, see what an IID is.
How does using an IID work?
Follow the instructions for the specific unit installed in your vehicle. In a typical routine, the driver switches on the vehicle’s electrical system, waits for the device prompt, and provides a breath sample. If the sample meets the device’s starting conditions, the driver can start the engine. If it does not, the vehicle will not start, and the driver should follow the unit’s prompts or contact the provider for help.
Some programs require rolling retests after the vehicle is running. These are requested at intervals while driving to check that the driver remains compliant. Pull over safely if needed to provide a test; never handle the unit in a way that distracts from driving. If you cannot safely respond, prioritize road safety and follow the device and program instructions once safe. A rolling retest is distinct from a start-up sample, and requirements vary by program.
An IID may also record event information for required monitoring. What is recorded, how it is reported, and the consequences of a missed or failed test depend on the governing program. Ask the relevant authority or provider for rules that apply to your case rather than relying on assumptions from another state.
How is an IID different from a regular breathalyzer?
| Feature | Ignition interlock device | Standalone breathalyzer |
|---|---|---|
| Connection to vehicle | Installed and connected to the ignition system | Not connected to vehicle controls |
| Purpose | Allows a vehicle start only when a required sample meets the device conditions | Provides a separate breath reading for personal reference |
| Program monitoring | May record required events and be checked during service, according to program rules | Does not fulfill an IID monitoring requirement |
| Installation and upkeep | Requires professional installation and periodic service as directed | Does not require vehicle installation |
A separate breathalyzer reading is not legal clearance to drive. Do not drive after drinking or when you may be impaired. When an IID is mandated, only the approved installed device and the official program instructions address that requirement.
Who may be required to have an interlock device?
A court or motor vehicle agency may require an IID as part of a DUI-related restriction or reinstatement process. The order, license status, state, and case details affect the requirement. The device itself does not tell you when you are eligible to drive, how long the requirement lasts, or whether your driving privileges have been restored.
For Arizona drivers, confirm your individual requirements with the Arizona Motor Vehicle Division and any authority overseeing your case. Do not assume that a requirement or process from California or another state applies in Arizona. Arizona-licensed drivers should also confirm approved installation arrangements in Arizona; an out-of-state installation does not satisfy Arizona IID requirements.
California drivers should check their own DMV instructions and court paperwork. Budget IID serves select Arizona areas and Roseville, California; the available service location does not determine the legal conditions of an individual’s case. See Budget IID service locations to check the listed coverage.
What should you confirm before choosing an installer?
Before scheduling, gather the order or agency notice and verify exactly what device and provider requirements apply. Ask the agency if anything is unclear. Then discuss practical details with the installer:
- Is the provider authorized for the state and program that issued your requirement?
- What vehicle information is needed to confirm installation compatibility?
- How long should you plan for installation and the device-use demonstration?
- Where and how often must you return for calibration or monitoring?
- How do you reach support if the device displays an alert or does not work as expected?
- What should you do if the vehicle changes, needs repair, or will not be used?
- What are the complete charges and which services or events could lead to additional charges?
Keep copies of your order, appointment confirmation, service records, and any instructions you receive. Write down the next appointment date and ask how to reschedule before you miss it. For local installation information, review Phoenix IID service or the Roseville IID location, depending on where you need service.
What happens at installation and ongoing service?
A technician installs the equipment in the vehicle and explains how to provide a sample, respond to prompts, and care for the unit. Ask questions while the vehicle is at the service center. Before leaving, make sure you understand how to contact support and what to do when an alert appears. The exact installation procedure and time depend on the vehicle and appointment.
Interlock devices require service as prescribed by the applicable program and device instructions. During a service appointment, the provider may calibrate the device and handle required reporting. Do not skip or delay a scheduled appointment without first confirming the correct steps. The provider’s service schedule and the government program’s compliance period are related but not interchangeable: completing an appointment does not by itself establish that the full requirement is over.
For Arizona program information, consult the relevant agency and review Budget IID’s Arizona DUI program overview. For device service, see the calibration information. Always use current instructions for your specific device and case.
What if the device displays a warning or does not work?
Read the display and follow the instructions provided with your unit. If the warning is unclear, contact your provider before attempting an unapproved reset, disconnecting equipment, or changing the vehicle wiring. Keep a note of the time, message, and circumstances, and take a photo of the display if doing so is safe and allowed. Provider support can help explain the device-specific next step; the motor vehicle agency determines program consequences.
Do not try to bypass, disable, or tamper with an IID. If a vehicle problem or repair may affect the installation, ask the provider how to proceed first. See what to do during an IID lockout for device-focused guidance. A device alert or event is not necessarily the same thing as a formal agency decision, so confirm any official status or consequence with the responsible authority.
What details should you learn during installation?
A clear handoff helps turn an unfamiliar device into a repeatable routine. Ask the technician to demonstrate each step, then practice while parked until you can identify the prompt, provide a sample, and understand the basic response. Ask what the indicator lights or messages mean on your exact unit rather than relying on a generic video or another driver’s description.
Before you leave, confirm the service interval, the appointment location, and how to arrange the next visit. Put the due date on a calendar and save the provider’s contact information in your phone. Ask whether service requires an appointment and what information to bring. If your schedule or commute makes a particular service time difficult, raise that before the first due date rather than waiting until a deadline is close.
Think through ordinary vehicle use as well. If family members share the car, explain that the device must be used according to the program and that nobody should attempt to manipulate it. If the car will be parked for an extended period, ask the provider what to do with the unit and whether the required service schedule still applies. If you expect to change vehicles, ask how a transfer is handled and whether you need approval before making arrangements.
How can you compare the device and service routine?
Not every question is about the device’s appearance. A practical comparison should look at the complete routine: the required sample method, the service cadence, support access, and the steps needed when the vehicle is unavailable. Confirm which details come from the official program and which are provider procedures.
| Question to compare | What to verify | Why it matters |
|---|---|---|
| Sample routine | How to start a test and respond to prompts on the assigned unit | Reduces confusion during everyday use |
| Service calendar | Where calibration occurs and when the next visit is due | Helps you plan around work, school, and transportation |
| Support process | Who to contact for a device message or an unexpected vehicle issue | Prevents guesswork or unapproved changes |
| Program authority | Which court or agency answers questions about eligibility and compliance | Keeps device support separate from legal or licensing decisions |
For a driver comparing service locations, distance alone is not the whole picture. Consider travel time for installation and recurring visits, how appointment booking works, and what support is available if a warning appears outside business hours. Ask for answers in plain language and keep them with your case documents. You can also review questions for evaluating an IID service center before choosing where to arrange service.
What if your vehicle or schedule changes?
Contact the provider before changing vehicles, arranging major electrical work, or leaving the car unused for a long period. A new vehicle may require a separate installation appointment and confirmation that the setup fits the program requirements. Do not remove or disconnect the unit yourself. Ask what records or approval are needed, and confirm how to maintain compliance while the vehicle is being repaired or replaced.
If you rely on the car for work or caregiving, plan a backup ride for installation and required service visits. A typical installation includes both equipment work and an explanation of the unit, so reserve enough time rather than scheduling a tight connection. For help arranging a next step, use the Budget IID getting-started information and confirm the specifics for your vehicle and program.
Frequently asked questions
Can an interlock device start a car automatically?
No. The driver provides a breath sample when prompted. The vehicle’s ignition remains restricted until the device’s starting conditions are met. The driver still must follow license restrictions and all safe-driving laws.
Does an IID test the driver continuously?
No. A unit may request rolling retests at intervals while driving, depending on its configuration and program rules. It does not continuously measure a person’s breath. Follow prompts without compromising safe vehicle operation.
Can I install an IID myself?
A required device should be installed through a provider authorized for the applicable program. Professional installation connects the unit to the vehicle and includes instruction. Confirm the approved provider and process with the authority that issued your requirement.
Does getting an IID mean I can drive?
Not necessarily. Installation does not by itself restore driving privileges or replace any license, court, or agency conditions. Confirm your eligibility and restrictions directly with the relevant authority before driving.
Contact Budget IID about your next step
An interlock device is one part of a broader compliance process. Confirm your state and case-specific instructions, keep service appointments, and ask questions before acting if a device message or agency notice is unclear.