Breathing into your Intoxalock is simple and takes only a few seconds before you are able to start your vehicle. When you blow into the device, it registers your breath alcohol content (BrAC) to determine if it’s within the legal limits to start the car. If your BrAC is within your state’s legal limits, you will be able to start your vehicle; however, if your BrAC is above your state’s allowed limit, you will not be able to start the ignition.
Ignition interlock devices are extremely accurate at measuring all sources of alcohol, including those that could be found in some commonly used products. As an ignition interlock device user, you are responsible for educating yourself and refraining from using these products while operating your device.
As noted in state regulations, you are responsible for every above-limit BrAC that is registered. Many myths exist about false positives and what causes them, such as wearing perfume or cologne, refueling your vehicle and more. So why does this happen? And what causes it?
What can cause a false positive?
Intoxalock recommends that you do not eat or drink anything within 15 minutes of providing a breath sample into the device. Certain foods and beverages can contaminate your breath so that the device is unable to receive an accurate reading.
It’s also important to refrain from smoking cigarettes before or during the period of time you’ll be using your ignition interlock device.
While it’s rare to get a false positive, it can happen. One thing that is more likely to cause a false positive is mouthwash or sprays. Because mouthwash and sprays contain a high concentration of alcohol, they are able to register a higher BrAC, meaning your device won’t allow you to start your vehicle. The alcohol should dissipate within 15 minutes, so if you do use mouthwash or spray, wait 15 minutes before blowing into your device, choose a brand that is alcohol free or rinse your mouth with water.
What you should do
If you truly know that your ignition interlock is registering a false positive, keep blowing into the device. Positive BrAC readings from contaminants will dissipate much more quickly than a reading from alcohol you’ve consumed. It’s important to continue providing samples until a clean one is registered to show the dissipation. All ignition interlock providers hold you responsible for all BrAC readings, no matter the source.
Read our related content about How to Disconnect an Ignition Interlock Device.