Alcohol requires no digestion and gets absorbed from the mouth, stomach and intestine to the bloodstream. 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 surround 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 breathalyzer.

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.

Breath Alcohol Testing Technologies

A number of technologies are used to test breath sample for alcohol:

· Gas Chromatography
· Fuel Cell
· Semiconductor sensors
· Infra Red Spectroscopy
· Wet Chemistry