Alcohol Breath Tester Mistakes Poisoning for Alcohol Intoxication

Breath alcohol analyzers (Breathalyzer, Intoxilyzer, Alcosensor, Alcoscan and BAC Datamaster being common brand names) are prone to error, which can lead to serious legal problems. However, they can also lead to seriously mistaken medical diagnoses.

An apparently intoxicated middle-aged man was found in a public park. An alcohol breath analyzer (Intoxilyzer) recorded a 0.288 blood alcohol concentration (BAC). However, tests of his blood and urine were negative for beverage alcohol (ethanol or ethyl alcohol). He had consumed HEET Gas-Line 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 erroneous information?

Breath analyzer devices don't actually test blood alcohol concentration, which requires the analysis of a blood sample. Instead, they estimate BAC indirectly.

A major problem with some machines is that they not only identify the ethyl alcohol (or ethanol) found in alcohol beverages, but also other substances similar in molecular structure. 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 and 70 to 80 percent of them contain methyl group structure and will be incorrectly detected as ethyl alcohol.

The National Highway Traffic Safety Administration (NHTSA) has found that dieters and diabetics can have acetone levels hundreds and even thousand of times higher than that in others, causing false measurement of alcohol. Any number of products found in the environment can cause erroneous 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, and moisture; high body temperature; high ambient or surrounding air temperature; physiological differences between individuals; failure to to use the devices properly or to have the machines properly maintained and re-calibrated as needed.

The inaccuracies and errors of alcohol breath testers led one expert to assert that "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: avoid being a victim of a false alcohol breath tester reading by always staying well below the legal limit for blood alcohol concentration when operating a motor vehicle or use a designated driver.


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  • 2. Hlastula, M. Physiological errors associated with alcohol breath tests . The Champion, 1985, 9(6). Quoted in Taylor, L. Drunk Driving Defense. New York: Aspen Law and Business, 5th edition, 2000.


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