The Ignition Interlock Device (IID) is a breathalyzer for your car. While continuous alcohol monitoring (like a SCRAM bracelet) watches you 24/7, the IID is specifically designed to prevent “hot” starts and ensure you stay sober while behind the wheel.
“Blow Before You Go” – How it Works
- The Startup Test: Before your car will even click over, you must provide a breath sample. If your BAC is above the preset limit (typically 0.02%), the car will not start.
- Rolling Retests: To prevent someone else from blowing into the device for you, it will prompt you for random “rolling retests” while you are driving. If you fail or skip a test, your horn will honk and lights will flash until you pull over.
- The Logbook: The device records every test, every start, and every failure. This data is sent monthly to the Department of Revenue or your probation officer.
Estimated Costs in Missouri (2025-2026)
The IID is a lease, not a purchase. You are responsible for all associated fees, which typically include:
| Fee Type | Estimated Range |
| Installation | $0 – $150+ (Often waived with a lease, but hybrids/push-starts cost more) |
| Monthly Lease | $60 – $100+ per month |
| Calibration | $20 – $25 per monthly visit |
| Removal Fee | $50 – $130 at the end of your requirement |
Who Needs It?
- Mandatory: Anyone with two or more intoxication-related offenses on their record.
- Optional: First-time offenders can often choose to install an IID to drastically reduce their license suspension time.
- Camera Requirements: If you are under a 5-year or 10-year “denial,” Missouri law requires your IID to be equipped with a camera to verify who is providing the breath sample. This would increase the costs.
Statutes Cited: RSMo 302.304; 302.440
All Missouri statutes with “interlock” > click here
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