Breath-analysis machines detect and measure the ALCOHOL present in deep lung air and convert this to an estimate of BLOOD ALCOHOL CONCENTRATION (BAC). The basis for this calculation is the relatively constant though small proportion of alcohol that the body excretes through the lungs. BAC is approximately 2,300 times breath alcohol concentration, although there is some variation among individuals. Breath analysis machines use methods such as thermal conductivity and infrared absorption to detect alcohol in lung air. Because breath alcohol analysis is quick and non-invasive, it is a useful tool in a variety of situations. The breathalyzer has traditionally been associated with law enforcement agencies for monitoring drinking and driving. However, it is increasingly being used in clinical sellings. A number of models—both portable and fixed ones—are available.

The Breathalyzer breath test machine is the tradename of the model manufactured by Smith and Wesson, but the name...