Alcohol Breath Test Technology Under Attack

Posted Wednesday, November 13, 2019 by Andrew Charles Huff

One regular tool police use to investigate DUI cases is the Preliminary Breath Test (PBT) device, the small handheld device that officer have driver blow into to estimate the BAC. In Washington, a driver does not have to submit to a roadside breath test as it is purely optional. It is only the breath test machines at police stations that carry potential license revocations if you refuse to provide a sample. These devices are larger and produce more accurate results than the roadside PBT devices.

All blood alcohol content breath testing machines use either fuel cell or infrared cell technology, or both. The cell sensors on the machines oxidize the alcohol in the breath sample, which produces an electrical current that the breathalyzer is able to measure and translate into the percentage of alcohol in the persons system. This all sounds rather confusing but it may be enough to say that the alcohol in a person’s blood vaporizes and passes through the lungs. These organic compounds passing through the lungs are measurable as wavelengths of alcohol.

Breath test machines including the Draeger Alcotest used in Washington can produce inaccurate results. This may occur when the machine itself is not properly calibrated or defective. False-positive results may also appear on the machine due to the presence of alcoholic compounds in a person’s system that show up as ethyl alcohol molecules—the molecules that the breathalyzer detects—when, in fact, the alcohol molecules detected are part of the wider spectrum of methyl alcohol. Ethyl alcohol, the compound that is found in alcoholic drinks is only one molecule in a broader array of alcoholic compounds. For example, a person who suffers from certain medical conditions or who is taking a prescription medication may test positive on an alcohol detection breath test even though he or she has not been drinking.