Can Refueling Your Car Cause An Ignition Interlock Fail?

Ignition Interlocks, or car breathalyzers, have one job – to detect alcohol. And they’re good at that job. But if you have an interlock device installed in your vehicle you’ll need to know that alcohol can be found in a lot of places, — including your local filling station.

You probably already know that your interlock can react to residual food particles in your mouth, because things like bread and fruit can actually ferment and manufacture alcohol in your mouth. But there is another non-drinking source of alcohol you should look out for.

Occasionally users report that their ignition interlock registers alcohol when they start up after refueling their car or truck, even when they haven’t drunk anything and their mouth has been rinsed clean.

What’s happened is that ethanol fumes from the gasoline have seeped into the mouthpiece. It’s a small problem, and relatively rare, but here’s how to ensure that it doesn’t happen to you.

• Close vehicle windows and doors while refueling.
• Don’t operate the heater or A/C until you’re clear of the filling station. If they’re on, the ventilating fans could draw in fumes from outside.
• Windshield washer fluid has a high alcohol content, so it’s a good idea to keep the window closed for a short while if you’ve washed your windshield as well.

Getting a fail from ethanol fumes is pretty rare, but with the simple precaution of closing windows and doors, you won’t need to worry about it.