Principles of Testing

Alcohol requires no digestion and gets absorbed from the mouth, stomach and intenstine into the blood stream. When the blood goes through the lungs, the alcohol permeates from the blood to air in the deep lung region. The alveoli of the lungs are small tissue sacs surrounded by a fine network of capillary blood vessels, the thin membrane of the alveoli allows alcohol to enter the air. As alcohol in the alveoli air is exhaled, the concentration of alcohol can be detected by a breathalyser.

A Breath Alcohol Concentration (BrAC) is as accurate as the Blood Alcohol Concentration (BAC). The breath alcohol to blood alcohol ratio of 2100:1 is used for converting BrAC to BAC. This means that 2100mg of deep lung air will contain the same amount of alcohol as 1ml of blood.