Breathalyzer Mistakes Poisoning for Alcohol Intoxication

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 Breathalyzer 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?


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.

breathalyzer mistakesThe National Highway Traffic Safety Administration is the lead US 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 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 machines 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. They save many lives!

Breathalyzer Mistakes


1. Caravati, E. and Anderson, K. Breathalyzer mistakes poisoning by methanol for alcohol intoxication. Ann Emerg Med.

2. Hlastula, M. Physiological errors associated with alcohol breath tests. Champ, 9(6). Quoted in Taylor, L. Drunk Driving Defense.