BAC limits refer to the legal maximum Blood Alcohol Concentration that a person can have while operating a vehicle. In many places, a BAC of 0.08% is the standard limit for drivers aged 21 and over. This means that a person’s blood contains 0.08 grams of alcohol per deciliter. Exceeding this limit can lead to penalties, including fines and license suspension. Different regions may have varying BAC limits for specific groups. For example, commercial drivers often have a lower limit of 0.04%, while some states enforce a zero-tolerance policy for drivers under the legal drinking age of 21.