Although alcohol in mouthwash dissipates within 15 minutes, if you were to rinse your mouth, run out to your car, and give a breath sample, the device could very well register a positive reading for alcohol and your car won’t start.

Products such as mouthwash or breath sprays can cause significantly high readings on a breathalyzer because many of these products contain alcohol. For example, Listerine mouthwash contains 27% alcohol.

Mouthwash and Breath Strips: Most mouthwashes (Listermint®, Cepacol®, etc.) and other breath cleansing products contain ethyl alcohol. The use of mouthwashes containing ethyl alcohol can produce a positive test result.

So if you’re wondering “can mouthwash cause a failed interlock?” The short answer is yes. So if you just swish with mouthwash, and wait 20 minutes before blowing into your interlock, you should pass the test. That is, as long as you haven’t been drinking in the last 12-24 hours.

Because alcohol metabolism is different for everyone, there is no single answer as to how long a breathalyzer can detect alcohol in a person’s system, but in general, a breathalyzer can first detect alcohol in a person’s system about 15 minutes after it has been consumed and up to 24 hours later.

Since your body (and every body) metabolizes alcohol at 0.016% per hour, it will take 10 hours for a person with a BAC or 0.016 to reach a BAC of 0.00. In fact, you can determine BAC for each hour that you spend metabolizing alcohol.

The general “rule” is that it takes your body one hour to process one unit of alcohol. You should be okay with driving X number of hours after you have your final drink, where X is the number of units you’ve had.

As a rough guide, it’s around three hours if you drink one large glass of wine (250ml/three units), about two hours to break down a weak pint of beer, cider or lager (3.6% – few drinks are this weak any more), or three hours to break down higher-strength lager, beer or cider (5.2%).