In the context of breath alcohol testing, what is meant by “expired breath”?

"Expired breath" refers specifically to the breath that has already been exhaled. In the context of breath alcohol testing, this term is crucial because the analysis is conducted on the breath that leaves the lungs after being processed by the body.

When a person consumes alcohol, it enters the bloodstream and is eventually expelled from the body through respiration. The Intoxilyzer 9000 analyzes the amount of alcohol present in this expired breath to estimate the blood alcohol concentration (BAC). This process relies on the fact that the breath contains a proportional amount of alcohol to the blood, which is the basis for using breath samples in DUI testing.

The other choices do not align with this definition; inhaled breath, breath used for breathing, and breath taken during exercise do not pertain to the analysis used in breath alcohol testing and would not provide the necessary data for measuring alcohol content. Therefore, understanding that expired breath is the breath that has already been exhaled is essential for interpreting breath alcohol test results.