The Poison Review

BREATH ALCOHOL ANALYZER MISTAKES METHANOL POISONING FOR ALCOHOL INTOXICATION Caravati EM et al. Ann Emerg Med 2009 Oct 13 [epub ahead of print]

Abstract

This very interesting case report describes a false positive breath ethanol test erroneously indicating 0.288 g/210 L breath ethanol.  In the hospital blood ethanol was not detected; however, the serum methanol concentration was 589 mg/dl.  The breath test was done on an Intoxilyzer® 5000EN (CMI Inc). This is a rarely observed false positive result obtained by a breath alcohol analyzer.

The theory behind the false positive is that if a volatile compound has enough vapor pressure to pass from the blood into the breath, and absorbs infrared light at the same wavelength regions as the ethanol molecule,  a false reading may result.   This is a well written report with a good discussion of the breath analyzer.