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What are the mechanics behind breath test instruments?

| Oct 28, 2016 | Drunk Driving |

When a driver in New York is pulled over on suspicion of drunk driving, the police may ask the driver to take a breath test, in order to determine what the driver’s blood alcohol concentration is. If it is above 0.08 percent, it is above the legal limit and the driver may be charged with driving while intoxicated or DWI. However, it is not unknown for Breathalyzers to be faulty, leading to an incorrect result. New York residents concerned about this may want to learn more about how do Breathalyzers work in the first place.

First, it is important to understand how alcohol affects a person’s body. The type of alcohol we drink is called ethanol, and it is found in beer, wine and liquor. Ethanol molecules are not very big. This means that it is easy for them to be absorbed into a person’s blood stream from the time the alcohol hits the person’s stomach. Since ethanol is volatile and a person’s body is relatively warm, when a person inhales, some of the ethanol in his or her blood vaporizes into his or her lungs and is then exhaled out of the person’s body. The more ethanol in a person’s body, the more that is exhaled.

Organic compounds, such as ethanol, absorb infrared radiation at a certain wavelength. Infrared spectrometers inside Breathalyzers are set to the wavelength of ethanol. When a person blows into a Breathalyzer, their breath, along with the alcohol in it, goes into a chamber. Breathalyzers then begin to sample the person’s breath until the person breathes into the Breathalyzer for three seconds, allowing the Breathalyzer to get a consecutive reading.

A three-second breath ensures that deep lung air is being sampled, as this is where the greatest amount of ethanol in the person’s lungs will be. After that, the breath inside of the Breathalyzer’s chamber is analyzed by an infrared radiation detector, to detect how much ethanol has been absorbed. The Breathalyzer then displays the reading.

As this shows, Breathalyzers are actually quite complex instruments, and there are many steps along the way in which a mistake, error or malfunction could occur. Therefore, it is not impossible to contest the results of a breath test. By doing so, the accused may be able to show that he or she was not driving above the legal limit.

Source: Forbes, “How Does A Breathalyzer Test Work?,” Oct. 13, 2016

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