Breathalyzers

A breathalyzer (or breathalyser) is a device for estimating blood alcohol content (BAC) from a breath sample. more...

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"Breathalyzer" is the brand name of a series of models made by one manufacturer of these instruments (originally Smith and Wesson, later it was sold to National Draeger), but has become a genericized trademark for all such instruments. Intoxilyzer, Intoximeter, Alcotest, Alcosensor and Datamaster are the other most common brand names in use today. The U.S. Government's National Highway Traffic Safety Administration maintains a "Conforming Products List" of breath alcohol devices approved for law enforcement use .

Though technologies for detecting alcohol vary, it's widely accepted that Dr. Robert Borkenstein (1912-2002), a captain with the Indiana State Police and later a professor of Indiana University at Bloomington, is regarded as the first to create a device that measures a subject's blood alcohol level based on a breath sample. In 1954, Borkenstein invented his breathalyzer, which used chemical oxidation and photometry to determine alcohol concentration. Subsequent breathalyzers have converted primarily to infrared spectroscopy. The invention of the breathalyzer provided law enforcement with a non-invasive test providing immediate results to determine an individual's BAC at the time of testing. It does not, however, determine an individual's level of intoxication, as this varies by a subject's individual alcohol tolerance . And the BAC test result itself can vary between individals consuming identical amounts of alcohol due to race, gender, weight, genetic pre-disposition, metabolic rate, etc. Further, the assumption that the test subject's partition ratio will be average -- that there will be 2100 parts in the blood for every part in the breath -- means that accurate analysis of a given individual's blood alcohol by measuring breath alcohol is difficult, as the ratio varies considerably.

Breath analyzers don't directly measure blood alcohol content or concentration, which requires the analysis of a blood sample. Instead, they estimate BAC indirectly by measuring the amount of alcohol in one's breath. Two technologies are most prevalent. Evidentiary machines, used by policeforces, generally utilize infrared spectrophotometer technology. Hand-held field testing devices, less accurate but becoming increasingly popular with law enforcement, are based on electrochemical fuel cell analysis; used by officers in the field as a form of "field sobriety test", they are commonly called PBT (preliminary breath test) or PAS (preliminary alcohol screening).

There are a number of models of breath alcohol analyzers that are intended for the consumer market. These hand-held devices are less expensive and can be much smaller than the devices used by law enforcement, and are less accurate, but can still give a useful indication of the user’s BAC. Almost all of these devices use less expensive tin-oxide semiconductor alcohol sensors, which are not as stable as fuel cell sensors or infrared devices, and are more prone to false positives. Breath alcohol analyzers sold to consumers in the United States are required to be certified by the Food and Drug Administration, while those used by law enforcement must be approved by the Department of Transportation's National Highway Traffic Safety Administraion.

Read more at Wikipedia.org