An Explanation of Blood Alcohol Concentrations (BAC)

The legal definition of whether someone is intoxicated is the measurement of alcohol concentration in his or her blood.

Blood alcohol concentrations are determined by testing the level of alcohol present in a person’s blood. Alcohol is testable because it is not processed like other food products. When alcohol is ingested it is absorbed into the bloodstream. This absorption is what causes the alcoholic effect we call intoxication.

The blood-alcohol concentration (BAC) is expressed as a percentage. Here’s an example:

A BAC of 0.05% means that out of 10,000 blood component parts, five parts are alcohol.
Three types of tests are commonly used in determining blood alcohol concentrations: breath test, blood test, and urine test.