The concentration of alcohol in the lungs relates to the concentration present in the blood. By using a partition ratio, it is possible to determine the BAC almost instantly from the air a person exhales rather than requiring a blood sample. The ratio of breath alcohol to blood alcohol is roughly 2,100:1. This means that roughly 2,100 milliliters (ml) of breath will contain the same amount of alcohol as 1 ml of blood.
Using the partition ratio, a breathalyzer can calculate a person’s BAC. Generally, a breathalyzer can measure BAC due to a chemical reaction. The alcohol vapor in a person’s breath reacts with an orange solution known as potassium dichromate. When alcohol is present, this solution turns green. This color change creates an electrical current, which the breathalyzer can convert into a value to determine the BAC.
Generally, the BAC limit in the U.S. is 0.08%. However, in Utah, the limit is 0.05%. For an adult, a BAC of 0.08% may correspond to
