Last updated: August 2022

What’s a Breathalyzer & How Does It Work?

If you’re stopped by a cop who suspects you of drunk driving, one of the tools he or she will use to figure out how much alcohol you’ve consumed is a breathalyzer.

What's a breathalyzer? Simply put, a breathalyzer is a device that detects the presence of alcohol in your body — and it might steer you toward a DUI or a DWI.

So, how does this gadget work? When might a law enforcement officer ask you to blow into one? Also, once you do blow into it, what info does it spit out? Find out, with Direct Auto Insurance!

How does a breathalyzer work?

According to, a breathalyzer measures the blood alcohol content or blood alcohol concentration (BAC) in your bloodstream.

Now, we don’t want to get too technical, but a breathalyzer comes in three types:

  • a semiconductor oxide-based tester,
  • a fuel cell tester, and
  • a spectrophotometer.

Police officers most often use a fuel cell tester or a spectrophotometer.

The fuel cell tester is hand-held, portable, extremely accurate, and very sensitive. A fuel cell measures the amount of alcohol in your body by triggering a chemical process called oxidation. When the alcohol in a breathalyzer sample is oxidized, it creates an electrical current. The higher the amount of alcohol that’s oxidized, the greater the current is. This current gives a measurement of a driver’s BAC.

While a fuel cell breathalyzer can be used on the street, a spectrophotometer is a large device you’ll typically see on a desk at a police station.

Spectrophotometers identify molecules based on the unique way they absorb infrared light. The breathalyzer measures the level of ethanol, or alcohol, in your body to determine your BAC level.

When could you be asked to blow into a breathalyzer?

If you’re pulled over by a law enforcement officer during a routine DUI/DWI roadblock, when you’ve been driving recklessly, or after you’ve been involved in a car accident, the officer might ask you to take a breathalyzer test. If you refuse, you may be requested to undergo other tests at a police station or medical facility.

To learn specifics and understand your rights related to field sobriety and breathalyzer or other DUI/DWI tests, you should consult a local attorney who handles DUI/DWI cases.

What kind of info does a breathalyzer test give?

If you’ve taken a breathalyzer test, law enforcement officers will have a reading of your BAC. However, these test results may not always be accurate. According to BACtrack, a seller of breathalyzers, “Breath test results may help an officer determine if a subject should be arrested for suspicion of DUI, but results [of breath tests] are not always admissible in court.” That said, don’t buy into the myths that you can fool a breathalyzer by sucking on a penny or chewing gum, that won’t work. Instead, drink responsibly. Never drink and drive.

In all 50 states, a BAC above 0.08% can result in a DUI (Driving Under the Influence) or DWI (Driving While Impaired) charge. BAC isn’t the only factor that determines whether you’ll be convicted of DUI/DWI because legal circumstances vary.

No matter what kind of DUI/DWI charge involved, you should consult an attorney so you know your rights. If you are facing a DWI or DUI and your driver’s license is suspended, you might need to get an SR22 insurance form to get your license back. Find out more about expect from a DUI/DWI.

Getting back on track after a DUI/DWI isn’t the easiest thing to do. However, at Direct Auto, we can help you file an SR22 after a DUI, find affordable car insurance, and more. Call 1-877-DIRECT (1-877-463-4732), get a quote online , or come in for help with a DUI, insurance, or SR22 today!

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