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How does a Breathalyzer test work?

On Behalf of | Jul 22, 2021 | Criminal Defense |

If you’re stopped by the police and they ask you to take a Breathalyzer test, it’s a good idea to understand how these tests work and how they come up with their final readings. There are specific testing requirements that officers must abide by, and those requirements help make sure that your test comes back as accurate as possible.

Failing a Breathalyzer test at .08% or higher could mean losing your license and freedoms. Even at a lower level, the test results could be used against you in court.

Understanding a Breathalyzer’s functions

The most accurate police Breathalyzers are a kind of modified infrared spectrometer. One is used to determine your blood alcohol concentration. The tool recognizes the difference between different kinds of organic compounds, like ethanol, as those compounds reflect or absorb infrared light differently. The Breathalyzer test should be calibrated to identify ethanol, so that it reads the BAC accurately.

The other option, a fuel cell Breathalyzer, uses a chemical reaction to identify alcohol levels in the breath. These are often used by officers in the field, while IR testing is usually used at the police station instead. IR testing can also be used as a control to calibrate other systems.

Can Breathalyzers be wrong?

Breathalyzers absolutely can be wrong. The machinery can look for other kinds of substances, like isopropyl alcohol, acetone or methanol. All of these could impact the outcome of the test, since they’re forms of alcohol, too.

Can a Breathalyzer read mouthwash as alcohol?

If your mouthwash contained alcohol, then yes, a Breathalyzer test could read inaccurately if you used that mouthwash recently. However, the machine does read that there is more alcohol at the beginning of a reading compared to the end, so the reading should suggest that it was “mouth alcohol” instead of “blood alcohol.”

Since there is a risk of misreads, it is important for officers to give more than one Breathalyzer to those they’ve stopped. Usually, there is a waiting period of around 15 minutes between tests.

If your BAC test comes back high, it’s a good idea to start deciding on a defense. If you face DUI charges, then it’s time to look into ways to build a case against a conviction.