How does a Breathalyzer Work?

Whenever a Colorado driver spots the flashing red and blue lights in the rear view mirror, the pulse rate will inevitably increase, especially if the person has been drinking. Most Coloradans know that they can be required to submit to a blood test to measure the percentage of alcohol in their blood stream. One of the principal used by police in Colorado to make a field evaluation of a person’s level of intoxication is to ask the suspect to exhale into a small, hand-held device known as a breathalyzer. The device will then provide a numerical value (referred to as a blood alcohol count or BAC) that measures the suspects level of intoxication. If the reading exceeds the state maximum level of intoxication (0.08%). The question is how does this little device provide such an important number? Knowing how a breathalyzer works can be essential to attacking the evidence in court.

The Basics

The breathalyzer relies on chemical changes in a person’s breath caused by alcohol that generate an electric current. The greater the color change, the higher will be the defendant’s BAC. The subject of the test exhales into a chamber filled with potassium dichromate. The exhaled breath is what is known as aveolar air, that is, air that has passed through the subject’s lungs. A portion of the avolear air is directed to a chamber with little or no potassium dichromate, while another portion is directed to a chamber with a high percentage of potassium dichromate. The chamber containing the higher level of potassium dichromate will turn green, thereby generating an electrical current. The difference in color between the two chambers generates an electrical current that can be converted to a quantitative value for BAC. This value appears in the window on the breathalyzer and indicates the individual’s level of intoxication.

Challenging Breathalyzer Results

The readings made by a breathalyzer are obviously very sensitive, and any deviation from correct procedure can affect the final measurement of BAC. An experienced defense attorney can use these procedural deviations to call into question the outcome of the breathalyzer measurement. Such a challenge may persuade the judge to exclude the results of the breathalyzer test from evidence at trial.

Anyone stopped for a breathalyzer test should carefully the manner in which the police officers conduct the breath test. Any deviations should be described to the defendant’s attorney as possible grounds for excluding the results of the breathalyzer test.

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