In 1954, the first device for breath testing of blood alcohol levels was invented.
There are a variety of tests available for determining the blood alcohol content of any given individual. These methods base their results on measurements of alcohol concentrations in blood, urine, saliva, and hair samples. For law enforcement agencies, sobriety tests have included physical demonstrations, such as walking a straight line, or breath testing using a monitoring device called a breathalyzer. Its results are based on the physical release of alcohol molecules during respiration.
Blood and Alcohol
Before alcohol reaches a person's stomach, it is already being absorbed into the blood stream through the mouth and esophagus. Alcohol is unique in that it retains its molecular structure even after being absorbed into the bloodstream. As a person breathes, the blood flowing through the lungs expels both alcohol and carbon dioxide molecules. Based on a fixed ratio, the breathalyzer estimates the relationship of blood-alcohol-to-breath-alcohol concentration. The final result is judged according to a legal standard. The legal limit of blood alcohol concentration in all states is .08, meaning .08 grams of alcohol detected for every 100 milliliters of blood.
How It Works
The breathalyzer is an electronic device containing a fuel-cell gas sensor that detects alcohol molecules. When a person who has been consuming alcohol blows into the device through a tube, electrodes in the fuel-gas sensor oxidize the alcohol into acetic acid. Through a monitoring system that measures the numbers of protons and electrons released from the process, a signal is sent to a microprocessor in the unit that estimates the blood alcohol content of the individual being tested. The more electrons produced from the process, the greater the alcohol content of the sample.
Support for Use
As a method of apprehending drunk drivers, the breathalyzer is favored by law enforcement agencies for many reasons. The device allows a non-invasive means of testing drivers, as opposed to obtaining blood samples. This latter option would also require medically qualified personnel to be on the scene. It is portable and easily carried with officers in their cruisers as they are on patrol. Also, the speed of results contributes to the timely apprehension of suspected drunk drivers. Instead of waiting for hours for blood samples to return from a lab, officers can decide within minutes if a person might be legally impaired.
Opposition
Opponents dispute breathalyzer results as being inaccurate since they are not direct readings of alcohol content in the blood. They suggest that variations in breathing patterns can give fluctuating results. Holding one's breath before blowing into the device can increase an alcohol reading while hyperventilating can bring it down. Another argument is that other substances in a person's mouth, lungs or even in the air around him can skew the results. For example, tests have shown cigarette smokers should wait about ten minutes after their last puff to take a breathalyzer, or the results might provide a false positive. Opponents also suggest that inaccurate operation by officers, or the possibility monitoring units have not been properly maintained, contributes to false readings from the device.
