Does the Q.E.D. test measure residual alcohol in the mouth or is it measuring the alcohol within the entire body (blood stream)?

Beverage alcohol (ethyl alcohol) is absorbed directly and unchanged into a person’s body and is evenly distributed throughout the blood stream and other bodily fluids, including saliva. The Q.E.D. test measures the amount of alcohol in bodily fluids, commonly called blood-alcohol concentration, or BAC. Residual alcohol in the mouth just after a person takes a drink is quickly absorbed, swallowed, or evaporated.   A person’s mouth is “clear” of residuals 10 minutes after eating or drinking.