Arizona Ignition Interlock
How an Ignition Interlock Actually Works
Understanding the device is how you stay out of trouble with it. Here is exactly how it reads your breath, why it asks for retests while you drive, and how every event reaches Arizona MVD.
Most extensions are not from drinking — they come from misunderstanding the device: a missed retest in the driveway, a hot handset, a shop disconnect.
The Device, Step by Step
From the sensor chemistry to the nightly upload that reaches MVD — the moments flagged below are where clean drivers most often slip.
The Sensor — a Heated-Platinum Fuel Cell
An interlock does not guess. It uses a fuel-cell sensor built around a heated platinum element. When you blow into the handset, the device waits until it receives deep air from your lungs — not a shallow puff — and pulls that sample across the heated platinum. Any alcohol in the breath evaporates off the platinum and produces a small electrical charge. The more alcohol present, the stronger the charge, and that reading decides whether the engine will start.
The Startup Test
Before the engine will turn over, you provide a breath sample. Pass, and the car starts. Fail, and it will not start — and the failed attempt is logged. Because the cell is reading deep-lung air, it is sensitive to whatever is in your mouth at that moment, which is why residual mouth alcohol from food, drinks, or mouthwash can produce a positive that has nothing to do with impairment.
Rolling Retests While You Drive
Once you are on the road, the unit randomly prompts you to give another breath sample to confirm you are still sober. You pull the handset, blow, and keep going. A missed or failed rolling retest is recorded as an event — and these prompts are one of the most common ways a clean driver picks up a violation through a simple misunderstanding of timing.
The 2-Minute Window — and the Trap It Sets
Where people slipThe unit stays active for roughly two minutes after you shut the engine off. That is intentional: if your car stalls — say, on a railroad crossing — you can restart immediately without a full test. The catch is that if you switch the car off and walk into your house, the device may prompt a rolling retest while you are inside. Miss it, and it is logged as a violation. Stay near the vehicle until that window closes.
Every Night, It Talks to ADOT
Where people slipThe device records every test, every calibration, and every event, then uploads that data nightly to Arizona's ADOT servers, where violations and calibration status are tracked. There is no maybe-they-will-not-notice — a flagged event reaches MVD automatically. It also means a false reading you do not explain right away can harden into a confirmed violation before you have a chance to dispute it.
The Calibration Cycle
You return to the provider on a set schedule — typically every 30 to 60 days — so the device can be recalibrated and its stored data downloaded. Miss a calibration appointment and the unit can lock out, leaving the car undriveable until it is serviced. Calibration is usually bundled into your monthly fee.
Keep the handset out of the heat
Arizona temperatures affect the sensor. Take the handset with you rather than leaving it in a parked, baking car — temperature swings can skew a reading and turn a sober driver into a flagged event.
Want to know what actually counts against you? See interlock violations
Know the Device. Avoid the Violations.
The installer hands you a machine; it does not fight for you when it misreads. AES monitors your data logs, walks you through exactly how your unit behaves, and disputes false violations before they harden into MVD events. When something looks wrong, call AES — not the shop that put the box in.
Device Questions
How does an ignition interlock measure alcohol?
It uses a fuel-cell sensor with a heated platinum element. When you blow a deep-lung sample across it, any alcohol evaporates off the platinum and produces a small electrical charge — the more alcohol, the stronger the charge. That reading determines whether the car will start.
What is a rolling retest on an interlock?
While you are driving, the device randomly prompts you to provide another breath sample to confirm you are still sober. The unit also stays active for about two minutes after you shut the car off, so a stall lets you restart without a full test — but it can also prompt a retest after you have parked and stepped away.
Does the interlock report to Arizona MVD?
Yes. The device logs every test, calibration, and event and uploads the data nightly to Arizona's ADOT servers, where violations and calibration status are tracked. There is no wait-and-see — flagged events reach MVD automatically.
Why does heat matter for the handset?
Arizona temperatures affect the sensor. Leaving the handset in a parked, baking car can skew a reading, so it is better to take the handset with you. Temperature swings are one more reason a reading can look wrong without any drinking involved.
What happens if I miss a calibration appointment?
The unit can lock out and leave the vehicle undriveable until it is serviced. Calibration appointments are typically every 30 to 60 days, and the data download at each visit is what keeps your compliance record current with MVD.
Keep going across the interlock guide: the overview, who needs one and for how long, what it costs, violations, removal, and certified providers.
DUIINFO.NET is an educational resource, not a law firm. This page explains how the technology works in Arizona — it is information, not legal advice.