What is an ignition interlock device and how long do I need it?

The device requires a breath sample before the engine will start, and generally requires rolling samples while driving. Results are logged and reported.

When it's required varies. On a first conviction it can be ordered at the court's discretion, and becomes mandatory where the reading was substantially elevated or where a minor was in the vehicle. Second and subsequent convictions carry mandatory installation for progressively longer periods.

Practical points people don't anticipate. The device goes on every vehicle you operate, not just one. Installation and monitoring involve regular service appointments. Failed or missed samples are recorded and reported, and a pattern of them can extend the requirement or trigger a violation.

Certain foods, mouthwash, and other products can produce a positive reading, and the resulting log entry has to be explained.