Causes of false positives on breath tests and interlock devices

Causes of false positives on breath tests and interlock devices

| Oct 9, 2020 | Drunk Driving |

Authorities rely heavily on breath test devices to make arrests for driving under the influence. Courts may require ignition interlock devices in vehicles of people convicted of DUI to prevent drunk driving while still allowing them to get around. 

Unfortunately, these devices may not be as reliable as many people believe. Lifestyle choices and even health conditions can result in false positives. 


Cigarettes can cause an ignition interlock device to register a false positive. tells the story of a man in Virginia who reports five false positives over the course of a year on his IID that appear to relate to cigarette smoke. These positive readings have increased the time that he must keep the device installed on his vehicle and cost him approximately $1,500 in fines. 


Diabetes is a disease that affects the body’s metabolism. This can produce a condition called ketosis, in which the body, desperate for fuel, breaks down fats in the liver to release their energy. According to Men’s Health, this process gives off a form of alcohol as a byproduct, which a breath test or IID may detect when a person exhales. It is not the same kind of alcohol consumed recreationally, but some devices cannot tell the difference. 

Keto diet

In diabetics, ketosis is an unwanted side effect. However, people who want to lose weight using the keto diet plan meals in such a way that will induce ketosis intentionally. The idea is that burning fat stores for fuel will cause them to lose weight. False positives on breath tests are an unintended and often unanticipated side effect. 

Hand sanitizer

The most effective hand sanitizers contain at least 60% alcohol. While hand sanitizers can be an effective way of preventing the spread of disease, the alcohol fumes can linger in the enclosed space of an automobile and render a false positive on an IID.