A lot of stories circulate about ignition interlocks. Most of them are myths, but there’s one that’s true — though it’s nothing that you can’t handle easily if you have an ignition interlock installed on your car.

An ignition interlock, or car breathalyzer, prevents a vehicle from starting if the driver has been drinking. If you have a modern, up-to-date ignition interlock, such as one made by LifeSafer, the device is “alcohol-specific” — only alcohol can set it off and cause you to fail your breath test.

Here’s the catch: sometimes you can have alcohol on your breath and not know it. Certain foods contain or produce small amounts of alcohol, and while the amounts are not enough to impair your driving, the alcohol is right up near the mouthpiece, so its effect is exaggerated. Here’s what can trigger a fail, and what you can do about it.

Pizza and Pastries

It would have to be this category of foods, wouldn’t it? One of the most common culprits is yeast. Because it relies on the fermentation process to make dough rise, yeast produces a tiny amount of alcohol. In your stomach it won’t matter, but if you have a tiny bit of pizza dough, bread, cinnamon roll, or other bread-like food in your mouth, the alcohol could trip the sensor in an ignition interlock. Attention Homer Simpson: doughnuts are included.

Vinegar

Do you choose the salad instead of the fries? Good from a health perspective, but the vinegar in the salad dressing was probably made from wine, and traces of alcohol could still be around. Again, not enough to matter if you’ve consumed it, but if, as sometimes happens, you get a bit of lettuce snagged in your teeth, you could end up with a false positive.

Fruit & Fruit Drinks

If you remember your high school science, you know that fruit can ferment. Some fruit and fruit-based drinks can ferment and release just enough alcohol so that its presence in the mouth dings the interlock sensor.

Energy Drinks

The label on an energy drink says “alcohol-free,” but some of them contain a low concentration of ethanol. Be vigilant.

Vanilla Extract

Many people aren’t aware that the little bottle of vanilla extract at the grocer is at least 35% alcohol. You don’t use much in a recipe, but a few crumbs of that home-made sugar cookie could have enough to do the trick – if the trick is failing your breath test.

The Upshot: How to Prevent Food Fails

This one is easy. If you have eaten something on this list – or indulged in the other non-food culprits, mouthwash or cough medicine – just wait 15 minutes, or wash your mouth out with water before taking the test. Remember, the alcohol is just in your mouth, not your system. If your mouth is clean, you’ll blow a zero and be on your way.