In the United States, Breathalyzer measurement units are typically expressed as Blood Alcohol Concentration (BAC), which represents the amount of alcohol in a person's bloodstream. The most common unit used is:
Grams of alcohol per 100 milliliters of blood (g/100 mL)This is equivalent to percentage BAC, where a BAC of 0.08 means there are 0.08 grams of alcohol per 100 milliliters of blood (or 0.08%).
Source: BACtrack - bactrack.com/pages/breath-alcohol-units-of-measurement