Breath alcohol concentration is expressed as which of the following?

Breath alcohol concentration is expressed as which of the following?

• A. Parts per million of breath
• B. Grams per 210 liters of breath
• C. Percent by volume
• D. Milligrams per liter

Answer: (B)

Breath alcohol concentration is reported as grams of alcohol per 210 liters of breath. This fixed reference volume standardizes the amount of ethanol in the breath sample so results are comparable across tests and can be related to blood levels using the established breath–blood ratio. Using a set breath volume avoids variability from how much air a person exhales and aligns the reading with legal reporting conventions. The other expressions—percent by volume, milligrams per liter, or parts per million of breath—aren’t the standard units used by evidential breath testers.

Breath alcohol concentration is reported as grams of alcohol per 210 liters of breath. This fixed reference volume standardizes the amount of ethanol in the breath sample so results are comparable across tests and can be related to blood levels using the established breath–blood ratio. Using a set breath volume avoids variability from how much air a person exhales and aligns the reading with legal reporting conventions. The other expressions—percent by volume, milligrams per liter, or parts per million of breath—aren’t the standard units used by evidential breath testers.