Living with the device

Using an ignition interlock device: the blow is a skill

The unit is not only measuring alcohol. It is checking the sample came from deep lung air, and it verifies that by demanding a particular pattern — a long, steady exhale with a note behind it. Blow too softly, too briefly, or in bursts, and it rejects the sample before it ever reaches a reading.

Most people fail twice before the first sample registers. That is normal, it is not recorded as a failure, and it is entirely a matter of practice.

The rolling retest myth that causes real problems

You will be prompted, at random, to pull over and blow while the engine is running. Miss it or fail it and the device issues a warning, records the event, and sets off an alarm — lights, horn — until the ignition is switched off.

The engine does not cut out. Nothing in Ontario’s published material says the car stops, and it would be dangerous if it did. People who believe otherwise panic at the first prompt, and the panic is the actual hazard.

Ottawa winters are their own chapter

At −20 °C the handset wants warming before it reads reliably. Keeping it inside the car overnight rather than in a cold glovebox solves most of it. Budget an extra few minutes in January that you do not need in July.

False positives: what is true and what is not

Approved devices use alcohol-specific fuel-cell sensors, which are far better than the semiconductor sensors in novelty breathalysers — but they detect ethanol from any source, and they cannot tell where it came from. Mouthwash, some medications and yeast-containing foods can leave mouth alcohol that reads.

The fix is unglamorous: rinse with water, wait ten to fifteen minutes. Mouth alcohol dissipates. And be clear that this is a reason to wait beforehand, never an explanation afterwards.

Practise on someone else’s device

Every start, reading and rejected sample on your own unit is logged and downloaded to your provider every 60 days. The device in a training vehicle is on the school’s account, so the mistakes cost nothing. That is the whole argument for learning it before it is fitted.

Read the long-form version in how does an ignition interlock work. If a road test is part of your route back, we cover interlock car rental for a G2 or G road test and the ten-hour interlock training course. Related reading: Back on Track and remedial measures in Ontario and car insurance after a DUI in Ontario, or browse every Ontario DUI licence recovery article.