Blood Alcohol Content

Blood alcohol content or blood alcohol concentration (abbreviated BAC) is the concentration of alcohol (specifically ethanol) in a person’s blood.  BAC is most commonly used as a measure of intoxication for legal or medical purposes.  It is usually measured as a percent (mass of ethanol per mass of blood).   For breathalyzers, it’s assumed that the concentration of alcohol in a person’s breath is directly proportional to the concentration in their blood.

Alcohol is absorbed into your bloodstream primarily through the stomach and intestines.  The rate of absorption depends on many factors, including your weight, whether or not there is food in your stomach and your body’s rate of metabolism.  Deep within your lungs there are tiny blood capillaries that interface with the air.  This is where the alcohol in your bloodstream is evaporated into your exhaled breath.  The breathalyzer then determines the concentration of alcohol in your breath and converts it into an equivalent blood alcohol content reading.

Other ways that alcohol can be detected are through a saliva test, a blood test, or a urine sample.   Although alcohol can be identified using a breathalyzer, the most accurate results are those that are run in a lab, but they take much longer to determine.  If your breathalyzer BAC comes up at or above the legal limit, which is .08%, then a law enforcement official will typically run a lab test and forward your results to a court official.

The benefit of using a breathalyzer is that it can provide immediate blood alcohol content results.  A breathalyzer will not prevent a person from drinking and driving, but it’s a useful tool in determining if you are over the legal limit.

Unfortunately, the number of alcohol related deaths is still too high.  Knowing information about intoxication levels, blood alcohol content and simply your own limits can give you the information you need to make an educated and responsible decision.