Final answer:
A Preliminary Breath Test (PBT) may be requested under certain conditions related to alcohol consumption. Breathalyzers are portable devices used to measure the ethanol concentration in a person's breath, which is directly proportional to the blood alcohol level.
Step-by-step explanation:
A Preliminary Breath Test (PBT) may be requested under certain conditions related to alcohol consumption. In most countries, including the US, it is illegal to drive while under the influence of alcohol. Breathalyzers are portable devices used to measure the ethanol concentration in a person's breath, which is directly proportional to the blood alcohol level. When a measured volume of a suspect's breath is bubbled through a solution in a Breathalyzer, the ethanol is oxidized to acetic acid, and the solution changes color to indicate the amount of ethanol present.