Breath Testing Devices | Understanding The Evidence

If you have been arrested for a DUI in Washington State, it is likely you were asked to take a breath test.  These tests count as evidence against you in court and with the Department of Licensing.  Learn about the different test and the technology behind them below.

Datamaster and Draeger Breathalyzer Test Devices

BAC | Breath Test Device | Breathalyzer | Washington DUI Lawyers
DataMaster – BAC

There are two breath test instruments in use in Washington. For decades, the Washington State Patrol has used the Datamaster and Datamaster CDM breath test machines, manufactured by National Patent Analytical Systems for all Washington breath tests. This device uses a technology called infrared spectroscopy. Alcohol is one of a number of molecules that absorbs infrared light, and the Datamaster measures the amount of infrared light within the sample chamber that reaches its detector in order to come up with an alcohol measurement. The Datamaster machine is used by most counties in western Washington.


Some counties in northern and eastern Washington use the new, state of the art breath testing machine called the Draeger Alcotest 9510. The Draeger uses two technologies to measure alcohol on the breath. One of those technologies is the same infrared spectroscopy method used by the Datamaster. The IR technology of the Draeger is, however, more sophisticated than that used by the Datamaster because an additional “filter” is used to try to flag the presence of other chemicals on the breath that might cause a false positive. In addition, the Draeger uses a separate technology, an electrochemical fuel cell, to come up with a separate alcohol measurement. Because the fuel cell is sensitive only to alcohols, there is less potential for chemicals other than alcohol to cause a false positive result.

Breath Test Issues

Breath Test | Drager 9510 | Callahan Law, P.S., Inc.
Drager Alcotest 9510

Physiological differences between people in the population, such as lung capacity and breathing pattern, to name a few, will cause natural differences in the accuracy and reliability of breath test results. It is also very important to the accuracy of the test that the operator of the breath test machine administer the breath test itself as well as the pre-test mouth check and “observation period” correctly. Unlike the WSP breath test technicians who maintain and repair Washington breath test machines, breath test operators do not have in-depth training on how the machines work. Most law enforcement officers around the state are certified to operate machines in their area, but their ignorance of the science involved and their relative inexperience in breath testing can cause mistakes during the test administration process that might seriously compromise the value of the results of the test.


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Washington DUI Lawyers | Callahan Law, P.S., Inc.

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