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How does a breathalyzer work?

Last Updated: Apr 17, 2019 09:19AM PDT
Most breathalyzers use one of three technologies to detect Blood Alcohol Content (BAC), which is the concentration of alcohol in a person's blood: a semiconductor oxide sensor, a fuel cell sensor or an infrared spectrometer.

Semiconductor oxide-based testers, such as the BACtrack Vio or BACtrack Go Keychain Breathalyzer, are relatively new and very affordable. An ethanol-specific MicroCheck® sensor is used to measure the subject's BAC. Semiconductor oxide sensors offer many benefits, including low cost, low power consumption and small size. When used for personal, home and low-volume professional testing, semiconductor oxide models have been proven to perform very well and provide accurate readings.

Fuel cell testers, such as BACtrack Professional Grade Breathalyzers, offer extremely high accuracy and sensitivity, in addition to being handheld and portable. In over 30 US states, roadside testing is now permitted using fuel cell testers. A fuel cell measures alcohol content by creating a chemical reaction that oxidizes the alcohol in the sample and produces an electrical current. The more alcohol that is oxidized, the greater the current. The current is measured to determine the subject's BAC.

Infrared Spectrometry is used in large, table-top breathalyzers often found at police stations (and in BACtrack's quality control lab). Spectrometers work by identifying molecules based on the way they absorb infrared light. The level of ethanol in a sample is singled out and measured, and a subject's alcohol level can then be determined. BACtrack does not sell spectrometers, but we do use them for quality control testing

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