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How accurate are breath test results?

On Behalf of | May 31, 2022 | DUI

If law enforcement has pulled you over on suspicion of drinking and driving, you know firsthand the overwhelming emotions that can accompany such a situation. Law officers in Alaska and throughout the country use roadside breath test devices to measure a driver’s blood alcohol content level. This helps them determine whether you are driving with a BAC level over the legal limit of 0.08.

While handheld breath test devices are convenient and easy to use alongside roadways, they may not produce reliable results. In fact, some readings may be inaccurate and inflated to the point where it could lead to a wrongful DUI charge.

How do breath test machines work?

When you exhale a breath sample into the handheld device, the machine detects the amount of ethanol alcohol present in the sample. It then converts that number to a blood alcohol content level without measuring your blood at all. According to researchers at the State University of New York at Potsdam, breath test readings can vary by 15% when compared to actual blood concentration measured by a blood test.

What affects machine reliability?

In addition to ethanol alcohol, breath test devices also detect other substances that have similarly methyl group structures. Furthermore, environmental factors can also influence the results. The following can affect breath test machine readings:

  • Temperature and humidity of the air
  • Dirt, cigarette smoke and pollution in the air
  • Fumes from gasoline, cleaners and paint thinner
  • Residual blood, food, drink or vomit in the mouth
  • Eating certain foods, such as bread, before the test
  • Electrical interference from officer radios’ and cellphones

The machine does not provide accurate results if it is not calibrated properly and if the officer does not use the device correctly. At least one in four people who use a roadside breath test device will have elevated results and may receive a DUI as a result, according to researchers. Understanding how breath test devices work can help minimize your risk of getting a wrongful DUI charge and possible conviction.