How Do Alcohol Breath Tests Work?

Breath testing machines are commonly used to estimate a person’s blood alcohol concentration (BAC) before an arrest. Colorado law enforcement officers typically use an Intoxilyzer 5000, which is a particular brand of breath-testing machine.

All breath testing machines work on the principle that alcohol, once it’s ingested, enters the bloodstream through the walls of the digestive tract. Once it’s there, the alcohol travels with the blood throughout the body, including into the lungs, where the blood drops off carbon dioxide and picks up oxygen as you breathe. Some of the alcohol in your blood leaves the body as you breathe out, along with the carbon dioxide.

The Intoxilyzer uses infrared (IR) spectroscopy to sense the number of alcohol molecules in a breath sample. Since alcohol molecules have a different weight and shape than carbon dioxide or any other molecule in human breath, the IR spectroscope inside the Intoxilyzer machine can be calibrated to “see” these molecules while ignoring others in the sample. The machine then measures the number of alcohol molecules it “sees” against the total sample size to determine what percentage of the sample is alcohol. This number estimates the percentage of the test-taker’s blood that is alcohol. A person with a BAC percentage of 0.08 or higher is prohibited from driving under Colorado law.

The Intoxilyzer is a piece of precision equipment that must be calibrated, tested, and maintained regularly in order to give accurate test results. If you have been charged with drunk driving in Colorado, the experienced Colorado DUI lawyers at The Bussey Law Firm, P.C. can help you build an aggressive defense that fights for the best possible outcome in your case. For a confidential consultation, call us today at 719-475-2555.

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