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How do breath tests compare to blood tests?

On Behalf of | Mar 31, 2020 | DUI | 0 comments

Pennsylvania law enforcement officers use several different methods to determine whether a driver is operating a vehicle while intoxicated, including roadside breath tests. These small devices measure drivers’ blood alcohol content level; however, studies show that breath test results may not be reliable and accurate.

Researchers from the State University of New York at Potsdam compared the blood alcohol content results from breath test devices to those obtained from actual blood tests and found a variance of at least 15%. Furthermore, at least one in four people tested had inflated breath test results, which could lead to a wrongful DUI arrest and possible conviction.

While blood tests measure the amount of alcohol found in an actual blood sample, breath test devices measure the presence of ethanol alcohol found in an exhaled breath sample. The problem lies in the fact that breath test devices often pick up substances with similar methyl structures. Some of these substances may be found in human saliva.

Other factors that may influence blood alcohol content level readings include the following:

  • Gasoline, paint and cleaner fumes
  • Residual vomit, blood, food and drink found in the mouth
  • Relative humidity of the air
  • Temperature
  • Static interference from cellphones and police radios
  • Cigarette smoke

In one study, a participant, wearing a protective mask, spent 20 minutes painting a room. The participant then took a breath test and showed results of .075, all without consuming any alcohol. If you are asked to take a roadside breath test, keep in mind that the result may not be fully accurate.



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