Testing for blood alcohol content has been in practice since 1938, when Rolla Harger, a professor at Indiana University, invented the first tester, called the Drunk-O-Meter. This invention came at the close of Prohibition, when alcohol problems arose because of the widespread availability of alcoholic beverages, according to the Breathalyzer website. The Drunk-O-Meter involved blowing air into a balloon, and then infusing a chemical solution with this air--if alcohol was present, the chemical solution would change color. Although many advances have been made in blood alcohol testing, there are still problems with available testing methods.
Handheld Machine Inaccuracies
According to Dr. David J. Hanson, contributor to the State University of New York at Potsdam website, handheld breathalyzers use various methods to estimate blood alcohol content, but do not measure alcohol content directly. Direct testing requires a blood sample, notes Hanson. Varying methods may lead to different estimates. Also, several factors can interfere with testing results, such as tobacco smoke, signals from cell phones, gasoline, and blood and vomit in the subject's mouth.
Blood Test Inaccuracies
When blood tests are conducted to determine alcohol levels, the blood is typically drawn without an anticoagulant, so the concentrations analyzed are considered serums, according to Walter J. Frajola, contributor to the Clinical Chemistry website. Serum alcohol concentrations can be as much as 20 percent higher than blood alcohol concentrations, leading to an elevated test result. Many laboratories apply a mathematical averaging factor to test results to estimate blood alcohol level; however, body weight and other factors can create different ratios of serum alcohol to blood alcohol in each individual. This means that unless the subject could be correctly classified as an "average" person, applying the mathematical averaging factor could render the result inaccurate.
Methyl Alcohol Measurement
Breath alcohol testers are meant to estimate the level of ethyl alcohol, the type of alcohol found in beer, wine and liquor, in the subject's bloodstream. However, according to Dr. Hanson, these tools also detect other compounds that may be present in the subject's breath. Up to 80 percent of the natural compounds that may be present in the mouth contain methyl alcohol, which is not present in alcoholic beverages. Since methyl alcohol is similar in molecular structure to ethyl alcohol, the presence of compounds that contain methyl alcohol may cause false-positive readings.
