The breath machine is supposed to receive and measure alcohol from the deep lung tissue, a region of the lungs called the alveoli. Breath alcohol concentration from this “alveolar air" or “deep lung air” is thought to correlate with blood alcohol concentration.
But GERD can cause alcohol to travel from the stomach back to the throat and mouth. When this happens, the suspect blows this mouth alcohol (rather than alveolar air alcohol) into the breath machine. The machine then provides a reading higher—often times dramatically higher—than the DUI suspect's true BAC. A person with a true BAC of .05 can read .20, which turns a case that would not be charged into a criminal case.
This problem is not limited to those who suffer from regular or chronic GERD. Anyone who recently ate a large meal, a greasy meal or a spicy meal may experience acid reflux or heartburn. If you take a Datamaster breath test during this period, the results may be erroneously high.