Ignition Interlock Device (IID) Guide
Required after most DUI convictions, an ignition interlock device prevents your car from starting if it detects alcohol. Here's everything you need to know about choosing a provider, costs, and avoiding problems.
$70-150
Monthly Cost
Typical range
6-24 mo
Duration
Varies by state/offense
99.9%
Accuracy
Modern devices
IID requirements vary by state and offense. Check your state below for specific details.
What Is an Ignition Interlock Device?
An IID is a breathalyzer connected to your vehicle's ignition system. You must blow into it before starting your car—if alcohol is detected above the preset limit (usually 0.02-0.025% BAC), the car won't start. You'll also need to provide "rolling retests" while driving.
IID Guides
Everything you need to know about ignition interlock devices
Compare IID Providers
Three major providers dominate the market
| Provider | Locations | Coverage | Compare |
|---|---|---|---|
| Intoxalock | 4,500+ | All 50 states | View Details → |
| Smart Start | 2,200+ | All 50 states | View Details → |
| LifeSafer | 1,700+ | 48 states | View Details → |
Troubleshooting & Problems
Common issues and how to handle them
How an Ignition Interlock Works
Blow to Start
Before starting your car, blow into the device for 4-6 seconds. The device analyzes your breath for alcohol.
Pass or Fail
If your BAC is below the limit (usually 0.02%), the car starts. If above, it locks out for a timed period.
Rolling Retests
While driving, the device prompts random retests (typically every 5-30 minutes). Pull over safely to complete them.
Data Logging
All tests are recorded. At monthly calibration, data is downloaded and sent to your monitoring authority.
IID Requirements by State
Duration, exemptions, and approved providers vary by state
What Does an IID Cost?
Typical Costs
What Affects Cost
- Provider choice (compare quotes)
- State requirements (some mandate cameras)
- Vehicle type (some harder to install)
- Violation fees (if any occur)
- Duration of requirement
Sources & Official Resources
Information on this page is sourced from state DMV publications, IID provider documentation, and legal requirements. Always verify current requirements with your state DMV.
Last updated: January 8, 2026
Compare IID Providers
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