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Washington Breath Test Machines-What’s the Status?

Posted Friday, July 27, 2018 by Andrew Charles Huff

Washington has approved three breath testing machines for DUI investigations: 1) the Datamaster, 2) the Datamaster CDM, and 3) The Draeger Alcotest 9510. The first two machines, the Datamaster and e Datamaster CDM are being phased out in favor of the German-manufactured Draeger Alcotest 9510.

All three machines use a method called Infrared Spectroscopy to measure a sample of breath for its alcohol content. The Draeger Alcotest 9510 uses an additional method called electrochemical cell technology.

The basic operation of infrared breath testing devices is quite simple. You blow into the device and a sample of your breath is captured in a “sample chamber.” If you’ve consumed alcohol, that sample of your breath not only contains air, but it also contains alcohol molecules. Once the machine has a sample of your breath, a light is shone through the sample chamber – through the sample of your breath – and is detected by a photocell at the other end of the chamber. The alcohol molecules in your breath will absorb some of the light, so not all of the light will make it to the photocell. The machine then calculates the difference between how much light reaches the photocell when there is nothing in the sample chamber and how much light reaches the photocell with your breath in the sample chamber.

This process provides an indirect measurement of your blood alcohol content because the machine is testing your breath, not your blood. The blood alcohol content is obtained by applying a presumed “blood/breath partition ratio”. This partition ratio is based on the assumption that there is a fixed ratio between the alcohol concentration in the blood and in the air in the lungs. In the 1950’s, scientists determined that a ratio of 2100 to 1 was the best estimate of the blood/breath ratio for most of the population. That is, for every gram of alcohol in the air above the blood, there are 2100 grams of alcohol in the blood.

Both the Datamaster and Datamaster CDM have been used in Washington for years. However, many of these machines are so old that the manufacturer no longer provides parts for repair. When they break down or require parts to be changed, the Washington State Patrol must find spare parts on other unused machines until ALL breath test machines have been replaced by the Draeger Alcotest 9510.

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