What Are the Causes of False Positives on a Breathalyzer?

DUI Stop
••• aijohn784/iStock/Getty Images

Related Articles

The most common way for a law enforcement officer to measure blood alcohol concentration (BAC) in the United States is with a breathalyzer, an electronic device that measures the amount of alcohol in an individual’s bloodstream by taking a sample of his breath. Readings taken by police officers with breathalyzers are admissible in court and can be used to convict someone of driving while intoxicated (DWI). Under most circumstances, a driver whose BAC is at the legal limit of 0.08 percent or higher may be charged with drunk driving.

False Breath Test Results

Generally, breathalyzers have a margin of error of about 15 percent, but this can be as high as 23 percent. There are a few causes that could turn up false positive results, such as medications that increase BAC levels and the consumption of certain foods. When an individual is facing a charge of driving under the influence, or DUI, he may be able to fight the charge by providing evidence that it is based on false breathalyzer test results and that he was not drunk when he was tested.

Certain Personal Hygiene Products

Many personal hygiene products contain alcohol. These include:

  • Perfumes and colognes.
  • Mouthwash.
  • Breath sprays.
  • Body sprays.
  • Toothpaste.
  • Hand sanitizers.
  • Aftershave.
  • Bleach.
  • Air freshener fluid.

These products can cause false positive breathalyzer test results because a breathalyzer is designed to record alcohol fumes. Because these products contain alcohol, their fumes are recorded by the breathalyzer, even if the product is simply on the driver’s skin, as is the case when cologne triggers a false breathalyzer positive result. Similarly, fumes from insect repellant can cause a breathalyzer to show a false positive reading.

Specific Types of Food Affect Breath Testing

Eating certain kinds of food can also lead to a false positive on a breathalyzer test. These include food that contains alcohol, like ​penne alla vodka​ and ​coq au vin​, as well as foods that contain a high level of yeast, which can be found in certain baked goods. When yeast ferments, it turns sugar into alcohol. This is the process used to make alcoholic beverages, but it can also occur during the baking process, which can create a trace amount of alcohol.

Other foods that can potentially impact breathalyzer readings include:

  • Fermented sodas.
  • Ripe fruits.
  • Hot sauces.
  • Energy drinks.
  • Nonalcoholic beer and wine.
  • Protein bars.

Various Medical Conditions

Some medical conditions, like heartburn or acid reflux, lead to false breathalyzer results in certain ways. One is by increasing the amount of acetone in an individual’s breath. Although there is a trace amount of acetone in all human breath, diabetics experience an increase in acetone levels when their blood sugar levels drop. An individual with an elevated amount of acetone in her breath can face false breathalyzer results, especially if she has consumed an alcoholic beverage or recently used mouthwash.

Gastroesophageal reflux disease, or GERD, can also lead to false breathalyzer results because the condition pushes stomach gases into the throat and mouth from the esophagus. These gases contain methyl compounds, which can trigger a positive test reading on a breathalyzer.

Certain Types of Medications

Various medications can increase the BAC reading, including:

  • Cold medicines.
  • Allergy pills.
  • Certain anti-ulcer medications.

In addition to medications that increase alcohol levels, other medications can affect breathalyzer results without necessarily changing the driver’s BAC. Medications that affect breathalyzer results in this way include:

  • Oral gels used to treat toothaches.
  • Asthma medications.
  • Certain vitamins.

A person who takes medications that affect breathalyzer results can take care to reduce the chance of facing a false reading or inadvertently increasing her BAC by carefully following her doctor’s instructions regarding alcohol consumption while taking a specific medication. Many medications are adversely impacted by alcohol.