Breathalyzer Mistakes Poisoning for Alcohol Intoxication

Breathalyzers (alcohol brearth testers) are prone to error. This can lead to serious legal problems. However, they can also lead to seriously mistaken medical diagnoses. Case in point. A breathalyzer mistakes poisoning for alcohol intoxication.

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


Breath analyzer devices don’t actually test blood alcohol concentration. That requires the analysis of a blood sample. Instead, they estimate BAC 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 . Therefore, and will be incorrectly detected as ethyl alcohol.

breathalyzer mistakesThe 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 causes false BAC readings. Any number of products found in the home can cause false BAC results. These include compounds found in lacquers, paint removers, celluloid, gasoline, and cleaning fluids.

Other common things that can cause false readings of BAC levels are

  • 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  breathalyzer 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.

References: Breathalyzer Mistakes

  • 1. Caravati, E. and Anderson, K. Breathalyzer mistakes poisoning by methanol for alcohol intoxication. Ann Emerg Med, Oct 15, 2009.
  • 2. Hlastula, M. Physiological errors associated with alcohol breath tests . The Champion, 1985, 9(6). Quoted in Taylor, L. Drunk Driving Defense. NY: Aspen, 2016.