You’ve done everything right — completed your DWI requirements, installed the ignition interlock device, and stayed sober. Then one morning, your ignition interlock test fails, and you’re locked out of your car. You know you didn’t drink, so how could this happen?
If your ignition interlock test fails even though you weren’t drinking, don’t panic; we are here to help. Contact our attorneys today.
How the ignition interlock program works
Minnesota’s Ignition Interlock Device Program, run by the Minnesota Department of Public Safety (DPS), allows drivers convicted of DWI to regain limited or full driving privileges — as long as they can prove sobriety through regular breath tests.
Here’s how it works:
- You must blow into the interlock device before starting your vehicle.
- The device measures your blood alcohol concentration (BAC).
- If your BAC reads 0.02 or higher, the vehicle won’t start.
- The device may also request rolling re-tests while you’re driving to ensure ongoing sobriety.
If you fail a test, the device logs it and sends data to DPS or your interlock provider. Too many failed tests can trigger an extended interlock requirement or program violation — even if you weren’t drinking.
For more details, visit Martine Law’s Minnesota DWI defense page.
Common causes of false positives
You don’t have to drink alcohol to get a positive interlock reading. The devices are extremely sensitive and can detect trace amounts of alcohol from everyday products.
Here are the most common culprits:
1. Mouthwash or breath spray
Many brands contain ethanol or isopropanol, which the device can detect as alcohol for up to 15 minutes after use.
2. Fermented or yeast-based foods
Items like ripe fruit, pizza dough, kombucha, or energy drinks can cause a short-term alcohol reading.
3. Cough syrups or liquid medications
Over-the-counter cold medicines often contain small amounts of alcohol that can trigger the device.
4. Hand sanitizer or cleaning products
The vapors from alcohol-based sanitizers or disinfectants can be inhaled or transferred to your hands, affecting the test.
5. Mouth contamination
If you eat, drink, or use certain hygiene products before blowing into the device, residual alcohol in your mouth can cause a false reading.
6. Environmental exposure
Paint fumes, gasoline, perfume, or other strong chemicals can sometimes cause interference with the sensor.
Even if your BAC is actually 0.00, mouth alcohol or environmental contamination can cause a spike that reads much higher.
What to do if your interlock test fails
If you weren’t drinking, take these steps immediately:
1. Don’t panic — and don’t keep blowing right away.
Wait 10–15 minutes to clear any residual mouth alcohol, then retest. A second test showing 0.00 can help prove the first one was a false positive.
2. Document everything.
Write down:
- The time and date of the failed test.
- What you ate, drank, or used before testing.
- Any relevant environmental factors (cleaners, sanitizers, medications, etc.).
3. Notify your interlock provider.
Call your ignition interlock vendor as soon as possible. They can log the issue, download your data, and help confirm it was not due to drinking.
4. Avoid using alcohol-based products before testing.
For the remainder of your program, avoid:
- Alcohol-containing mouthwash, hand sanitizers, and medications.
- Eating or drinking anything 15–20 minutes before a test.
5. Inform your attorney if the state contacts you.
If the Minnesota Department of Public Safety or your probation officer accuses you of a violation, your attorney can present evidence showing the test result was inaccurate or caused by external factors.
What happens after a failed interlock test
The consequences depend on the type of failure and your prior record.
Start-up test failure
If your car doesn’t start because of a failed test, the system logs it but typically doesn’t count as a violation if you test again and pass.
Rolling retest failure
If the device detects alcohol while you’re driving, it logs a major violation — even if you weren’t drinking.
The Minnesota DPS may respond by:
- Extending your interlock requirement by 30–180 days,
- Requiring you to appear for a violation hearing, or
- Revoking your limited driving privileges altogether.
Your attorney can challenge these sanctions by showing your BAC dropped to zero within minutes or presenting evidence of environmental interference.
Proving you weren’t drinking
To protect yourself after a false positive, your attorney can gather and present:
- Device data logs showing rapid BAC drop-off.
- Maintenance and calibration records to check for malfunction.
- Witness statements verifying you were sober.
- Medical or lab tests (e.g., blood test showing no alcohol).
Minnesota courts recognize that ignition interlock devices can malfunction or produce false readings, so credible evidence can help you avoid penalties.
For guidance on building a strong defense, visit Martine Law’s criminal defense page.
How to prevent future false readings
Follow these practical steps to avoid future ignition interlock problems:
- Rinse with water before every test.
- Wait 15 minutes after eating, drinking, or brushing your teeth.
- Avoid alcohol-based hygiene products or medications.
- Keep your hands clean of sanitizer before testing.
- Ensure good airflow — avoid testing in enclosed spaces with chemical vapors.
- Keep a logbook to track any unusual readings or issues.
These habits can protect your record and make it easier to prove good-faith compliance.
Key takeaways
- False positives on Minnesota ignition interlock devices are common and don’t automatically mean you were drinking.
- Alcohol-based products, medications, and environmental factors can trigger temporary readings.
- Always document and retest after a failed reading.
- Report any issues to your interlock provider and attorney immediately.
- With proper documentation and legal help, you can avoid violations and stay on track with your license reinstatement.
If your ignition interlock test failed even though you hadn’t been drinking, don’t try to handle it alone. A false reading can still lead to penalties unless it’s properly challenged. Martine Law can help you explain what happened, gather evidence, and protect your driving privileges.
Contact Martine Law today for a confidential consultation with a Minnesota DWI defense attorney.
Disclaimer: This content is for informational and educational purposes only and does not constitute legal advice. For legal guidance specific to your situation, please contact Martine Law.