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Everything you need to know about false positives

Everything you need to know about false positives

Breathing into your Intoxalock ignition interlock 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 is an IID False Positive? 

In this case a false positive would be when your ignition interlock device detects an inaccurate alcohol content reading and consequently preventing your vehicle from starting. 

What can Cause a False Positive on my Ignition Interlock Device?

High quality interlock devices are extremely accurate and almost never detect an incorrect reading. The problem arises due to the sensitivity of the device. You would be surprised at how sensitive this test can actually be to the extent that it'll detect even the slightest fragments of alcohol. Intoxalock recommends that you do not eat or drink anything within 15 minutes of providing a breath sample into the device. 

Here are items you should avoid prior to breathing into your breathalyzer in car.

There are certain foods and beverages that can contaminate your breath so that the device is unable to receive an accurate reading which you most certainly must try to avoid.

  • Mouthwash: In most cases, mouthwash or sprays tend to 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.
  • Cigarettes: To be on the safe side, you want to avoid smoking a cigarette near the ignition interlock. Even though cigarettes don’t directly cause a false positive, there's a chance it may cause the device to malfunction, leading to false positives. 
  • Spicy Food: Eating spicy food right before breathing into your interlock device isn’t the best idea. Spicy food tends to produce methane gas into your stomach which may cause the device to denote a false positive. 
  • Energy Drinks: Low concentrations of ethanol may be present in some energy drinks which is why you should avoid consuming them right before you breathe into your vehicle’s ignition interlock device. 
  • Desserts such as Cookies: Shocking, right? You should avoid desserts such as cupcakes and cookies because sugar and yeast tend to create a small amount of alcohol which MAY be detected by your breathalyzer in car and result in a false positive. 
  • Low Carb Diet: This one usually gets overlooked, but a low carb diet can also become a reason for your ignition interlock device to indicate a false positive. Low carb diets tend to create acetones which can be falsely identified as alcohol. 

What you Should do

If you truly know that your ignition interlock registered a false positive, blow a new sample into the device after the countdown. 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.

If you need more information about an Intoxalock ignition interlock device, call our state specialists at (833) 623-0200.

Read our related content about How to Disconnect an Ignition Interlock Device.


Category: Drunk Driving
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