Texas Ignition Interlock: The Complete Guide
Everything nobody tells you about living with an interlock device in Texas.
$70-150
Monthly cost
6-24
Months required
30 days
Calibration interval
When Is It Required?
- •First Offense with BAC 0.15+: Mandatory interlock as condition of bond
- •Second+ Offense: Required for occupational license
- •ALR Suspension: May allow restricted license with interlock
- •Probation Condition: Judge may require regardless of BAC
How It Actually Works
Starting the car: You blow into the device for 2-4 seconds. If your BAC is below the threshold (usually 0.02-0.03%), the car starts. If not, it locks you out for a waiting period.
Rolling retests: While driving, the device will beep and require another test at random intervals (usually every 15-45 minutes). You have a few minutes to provide a sample. If you fail or miss it, the horn honks and lights flash until you pull over.
Data logging: Every test, every start, every fail is recorded and reported to your probation officer and the court.
The Stuff Nobody Warns You About
⚠️ False Positives Happen
Mouthwash, hand sanitizer, certain foods, and even some medications can trigger a fail. The device doesn't know the difference between alcohol in your mouth and alcohol in your blood.
Pro tip: Rinse your mouth with water before every test. Wait 15 minutes after eating or drinking anything before testing.
The Embarrassment Factor
Yes, people will see you blow into it. Yes, it's awkward. The device is visible on your dashboard. Rolling retests happen everywhere — at stoplights, in drive-throughs, in parking lots.
Reality: Most people don't know what it is. Those who do have probably been through it themselves.
Calibration Appointments
Every 30-60 days, you must bring your car to the provider for calibration and data download. Miss this appointment and your car may lock out completely.
Pro tip: Schedule appointments well in advance. Most providers have limited availability.
Cold Weather Issues
The device needs to warm up. In cold weather, you may need to wait several minutes before it's ready to accept a test.
Pro tip: Give yourself extra time on cold mornings.
⚠️ What Happens If You Fail
A fail is logged and reported. Multiple fails or a pattern can result in extended interlock period, probation violation, or worse. But a single false positive isn't the end of the world — you can often contest it with documentation.
Texas-Approved Interlock Providers
You must use a DPS-approved provider. Here are the major ones:
Intoxalock
Largest national provider
Smart Start
Good customer service reputation
LifeSafer
Competitive pricing
Draeger
German engineering, reliable
Guardian Interlock
Texas-based company
Low Cost Interlock
Budget-friendly option
Tips for Surviving the Interlock Period
- ✓Keep a water bottle in your car for mouth rinsing
- ✓Avoid mouthwash with alcohol — use alcohol-free brands
- ✓Wait 15 minutes after eating/drinking before testing
- ✓Keep your calibration appointments — set calendar reminders
- ✓If you get a false positive, wait the lockout period and retest
- ✓Document everything — keep a log of what you ate/drank before fails
- ✓Don't let anyone else drive your car
- ✓Consider getting a cheaper car for the interlock period
Total Cost Estimate (6 Months)
Information based on 2024 Texas DPS requirements. Providers and costs may vary. DUI911 is not a law firm.