Understanding Different Types of Preliminary Breath Testing Instruments

Preliminary breath testing, or PBT, is often used during a traffic stop by an officer who suspects that a driver may be driving under the influence of alcohol (DUI), but who does not yet have enough information to make an arrest. A driver whose PBT results show that his blood alcohol concentration (BAC) is over 0.08 percent may face arrest and charges of drunk driving. With so much at stake, it’s important to understand how PBT instruments work.

There are three basic types of preliminary breath testing instruments: infrared, wet chemical, and electrical. Each is designed to take a breath sample and calculate the amount of alcohol it contains, but the methods used may differ.

In an infrared PBT device, an infrared beam inside the device is calibrated to “see” alcohol molecules in a breath sample. The device measures the number of alcohol molecules it can “see” versus the total number of molecules in the sample, and then calculates a percentage. A wet chemical device, on the other hand, measures alcohol in a breath sample by measuring the amount of the sample that reacts with chromate salts, which will react to alcohol but not to most other substances commonly found in human breath.

Finally, electro-chemical or other electrical-based PBT devices, also use a reaction between alcohol and another substance. However, in these devices, the alcohol’s reaction with the substance produces an electric current, which the device reads. The stronger the current, the more alcohol is in the breath sample.

Understanding how PBT devices work is just one step in fighting for the best possible outcome in your case. At The Bussey Law Firm, P.C., our experienced Colorado DUI defense attorneys are familiar with PBT technology. They know how to examine test results and other evidence in your case thoroughly and how to build an aggressive defense on your behalf. For a free and confidential consultation, call us today at (719) 475-2555.

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