Final answer:
D.O.T. regulations require breath specimens for alcohol tests, and Breathalyzers are used to measure BAC by oxidation of ethanol which causes a color change in the device's chemical solution.
Step-by-step explanation:
According to Department of Transportation (D.O.T.) regulations, breath specimens are required for alcohol tests. The device used to measure alcohol content from breath is known as a Breathalyzer, which calculates blood alcohol concentration (BAC) based on the ethanol content in the breath. The Breathalyzer works by a chemical reaction where ethanol present in the breath is oxidized by the dichromate ion, leading to a color change from yellow-orange to green proportional to the amount of ethanol in the breath. This color intensity indicates the level of alcohol intoxication, which can have legal consequences, as driving with a BAC of 0.08% or higher is considered legally impaired. Blood alcohol levels can also be assessed by blood tests, although they are less frequently used for field testing.