Alcohol breath tests: gross errors in current methods of measuring alveolar gas concentrations.

Transitory contact of ethanol with the mucous membranes of the mouth or nasal passages, or both, is sufficient to drastically alter measurements of concentrations of ethanol in so-called "alveolar" gas for more than 20 minutes after such contact. Various concentrations of ethanol were taken into the mouth by human subjects and were expectorated. Readings of so-called "blood alcohol" were then taken at short intervals by means of the Breathalyzer(R) and were continued up to 1 hour after exposure. These readings were compared with blood-alcohol concentrations measured by quantitative chemical analysis of venous blood. When true concentrations of blood alcohol were at or close to zero (plus possible error of 0.0001 gram per 100 milliliters), readings of greater than 0.40 gram per 100 milliliters were obtained on the Breathalyzer. Repeated mouth washing and gargling with water, changes in the nature of the solvent, and stomach loading each had only a slight effect in diminishing these errors.