Not Medical Advice: As explained by Law Offices of Richard S. Lawson, residual mouth alcohol is one of the most common causes of a false positive result. Many things can cause residual mouth alcohol, including most mouthwashes, breath sprays, and cough syrups.
The U.S. Department of Transportation and the National Highway Traffic Safety Administration explains that after a person takes a drink, some of the alcohol remains in the mouth tissues. If the person exhales soon after drinking, the breath sample will pick up some of this leftover mouth alcohol. In this case, the breath sample will contain an additional amount of alcohol and the test result will be higher than the true BAC. Mouth alcohol remains in the mouth for roughly 15-20 minutes before dissipating.
Mouth alcohol can also be present for reasons other than a recent alcoholic drink. Chewing gum and dental appliances may retain alcohol. Some asthma inhalers contain alcohol. Further, if a person throws up prior to taking a breath test, they may have elevated mouth alcohol levels because the contents of the stomach are aspirated into the breathalyzer.
Many medical conditions can also artificially inflate breath test results. Diabetes is one such medical condition. The National Highway Traffic Safety Administration (NHTSA) has found that diabetics can have acetone levels hundreds and even thousands of times higher than that of other people.
An individual who suffers from gastroesophageal reflux disease, or GERD is also at particular risk of having an inflated breath test reading.
Even simple burping can interfere with the Intoxilyzer.
Environmental factors can also affect breath test results.