Breath Alcohol Testing Devices: How They Work

Get stopped by the police under suspicion of drunk driving and you will likely undergo a field sobriety test. That test will include seemingly simple tasks like walking a straight line and touching your nose. Fail the field sobriety test and the next step is a breath alcohol test. Known generically as a breathalyzer test, this test can analyze how much alcohol is in your system.

For years people have wondered exactly how breath alcohol testing devices work. How is it possible that an electronic gadget can measure the amount of alcohol is in a person’s system by analyzing his or her breath? This post will explain it.

More About Breath Alcohol Testing

Breath alcohol testing dates back to the late 1940s when scientists discovered that it was possible to determine the alcohol content of a person’s blood by measuring the alcohol content in breath. The science is rooted in the understanding that the human body absorbs alcohol but does not digest it.

When you drink, alcohol is absorbed by your mouth, throat, stomach, and intestines. It flows almost immediately into your bloodstream and then throughout your entire body. And because alcohol is not digested, it remains in the bloodstream until the body manages to completely flush it out.

This reality makes it fairly easy to determine blood alcohol content by analyzing a blood sample. But that is not what happens during a breath alcohol test. No blood is drawn. However, blood draws are not necessary thanks to the fact that blood moves through the lungs as a person breathes. Alcohol from the bloodstream is deposited in the lungs and breathed out every time a person exhales.

The amount of alcohol in alveolar air (the air we exhale) is a known quantity compared to the amount of alcohol in the bloodstream. So if we can measure alcohol content in a person’s breath, we can extrapolate to determine how much alcohol is in that person’s bloodstream. That is exactly what breath alcohol testing devices do.

Three Kinds of Testing Devices

California’s Rock West Solutions explains that a breath alcohol testing device is essentially a sensor. They also say there are three types of devices, as follows:

  • Photoelectric Intoximeter – A device that relies on a chemical reaction to produce a change in color. The first breathalyzer was this kind of device
  • Intoxilyzer – A device capable of measuring alcohol content via infrared spectroscopy.
  • Alcosensor – A device that measures alcohol content via oxidation of alcohol on an electrode. It relies on technology similar to a fuel-cell.

The photoelectric intoximeter was the go-to DUI sensor for law enforcement during the early years of BAC testing. But it is an old technology that is rarely used these days. Most law enforcement agencies use intoxilyzer or alco sensor devices. The latter is considered the most accurate and repeatable.

State Breathalyzer Laws

It is hard to imagine that there is any law enforcement agency in the U.S. that doesn’t rely on breath alcohol testing to determine alcohol impairment. That said, different states treat breathalyzer tests differently. The laws in one state might be completely different from those in a neighboring state.

In some states, it is not lawful for suspects to refuse a breathalyzer test. Other states give suspects that freedom. Still, other states allow suspects to refuse breathalyzer tests in exchange for automatic suspension of driving privileges until their cases are resolved.

Regardless of where you live, a breathalyzer device can determine a driver’s blood alcohol content with relative accuracy. It is one of law enforcement’s most reliable sensors and one that likely saves lives.

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