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How do breath testing devices generate readings?

| Apr 5, 2021 | DUI

After a drunk driving arrest in Georgia, you might think you have few options but to accept the consequences that a conviction may bring. Evidence such as a breath test implying your intoxication may seem insurmountable. However, depending on the nature of the test, that may not be the case.

If the only test results that indicate a blood-alcohol content level above the legal limit came from a hand-held breath testing device (typically administered by a law enforcement officer on the side of the road), you may be able to mount a successful challenge as to the validity of that evidence. Doing so, however, requires that you understand how such devices generate measurements.

The pathway of alcohol from blood to breath

When you ingest alcohol, the actual type of alcohol going into your body is ethanol. This is a water-soluble compound, meaning that it can permeate the membrane linings of the organs of your gastrointestinal tract and enter into your bloodstream. Once ethanol is in the blood, the veins carry it throughout the body, eventually arriving in your lungs. A portion of the ethanol vaporizes when it comes in contact with the oxygen in your lungs. The assumption, then, is that the ratio of alcohol on your breath in your lungs and that still in your blood is in equilibrium.

The mechanics of breath testing devices

According to the Alcohol Pharmacology Education Partnership, breath testing devices assume that ratio between your blood and your breath is 2100:1 (the concentration of alcohol in your blood being 2100 times greater than that of your breath). However, in reality, your blood-to-breath ratio may range between 1500:1 and 3000:1. This wide range of variance contributes to a greater margin of error with breath testing devices, thus undermining their reliability.