Alcohol breath testers are prone to error. This can lead to serious legal problems. But they can also lead to seriously mistaken medical diagnoses. Case in point. A breath tester mistakes poisoning for alcohol intoxication.

Here’s the story. Police found an apparently intoxicated middle-aged man in a public park. A breath tester recorded a 0.288 blood alcohol concentration (BAC). Yet tests of his blood and urine were negative for alcohol. In fact, he had consumed  antifreeze, which is 99% methanol. The alcohol breath tester had falsely shown the poisonous methyl alcohol as beverage alcohol, ethanol. ¹

This false reading from an alcohol breath tester nearly led to the patient’s death. How can a breath tester provide such seriously false information?

Problem

Breathe analyzer devices don’t actually test BAC. That requires a blood sample. Instead, they estimate BAC. And they do so indirectly.

A major problem with some machines is that they don’t only identify beverage alcohol ( ethanol). They also identify similar  substances. These machines identify any compound containing the methyl group structure. Over one hundred compounds can be found in the human breath at any one time. About 70 to 80 percent of them contain methyl group structure.  So they will be falsely detected as ethyl alcohol.

The National Highway Traffic Safety Administration (NHTSA) is the lead U.S. traffic safety agency. It finds that dieters and diabetics can have acetone levels hundreds of times higher than that in others. This also causes false BAC estimates. Many products in the home can cause false BAC results. These include compounds found in lacquers, paint removers, celluloid, gasoline, and cleaning fluids.

Many other common things can cause false estimates of BAC levels from breath testers.

• • Alcohol, blood or vomit in the subject’s mouth.
  • Electrical interference from cell phones and police radios.
  • Tobacco smoke.
  • Dirt.
  • Moisture.
  • High body temperature.
  • High air temperature.
  • Physiological differences between people.
  • Failure to to use the devices properly.
  • Improper  maintained.
  • Failure to re-calibrated as needed.

The errors of alcohol breath testers led one expert to make a strong assertion. “Breath testing for alcohol using a single test instrument should not be used for scientific, medical or legal purposes where accuracy is important.” ²

The take-home message is simple. Avoid being a victim of breath tester mistakes. You can do so by always staying well below the legal limit for BAC when driving. You can also be or use a designated driver.

Resources: Breathalyzer Mistakes

Web Pages

• • Alcohol Breath Analyzer Accuracy
  • Forced Drawing of Blood without Warrant
  • Alcohol Breath Testers and DWI/DUI Conviction Rates
  • Tongue Studs and Breathalyzer Tests
  • Alcohol Breath Testers. False Readings
  • DUI Defendants and Alcohol Blood Tests
  • Unreliable Alcohol Breath Test Readings Rejected
  • Unreliable Alcohol Breath Tests in DWI/DUI Court Cases
  • DUI Tests Must Now be Accurate
  • Alcohol Breath Testers Challenged
  • New Alcohol Breath Test Challenged

Footnotes