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Breath test device results: Are they accurate?

On Behalf of | May 26, 2020 | DUI/DWI

Officers in New York and throughout the country use roadside breath test devices to determine motorists’ blood alcohol content levels. If you have been pulled over on suspicion of drinking and driving, an officer may have asked you to exhale through a tube in the device. 

Although the results of the device may lead to a DUI charge and subsequent conviction, studies show breath test device readings are not always accurate. While the device may show that you have BAC level of 0.08 or higher, it could be a false reading. 

Breath tests vs. blood tests 

Breath test devices measure the amount of ethanol alcohol in an exhaled breath sample. Yet when researchers compared the readings to the results taken from an actual blood sample, they noticed a significant discrepancy. In fact, the readings varied by more than 15% in some cases, as reported by the State University of New York at Potsdam. That means that more than 23% or one in every four people who take a breath test will show inflated BAC level results. 

Factors that affect readings 

Researchers also found that breath test devices detect more than ethanol alcohol. Other substances that have similar methyl groups can show up on breath tests as well. The factors that can alter readings include the following: 

  • Fumes from gasoline or household cleaners 
  • Cigarette smoke and/or pollution in the air 
  • Electrical interference from officer radios and/or cellphones 
  • Residual drink, vomit, blood or food in the mouth 
  • Relative humidity and temperature of the air 
  • Misuse of device by officer 

Breath test devices must be calibrated regularly to ensure more accurate readings as well.