Understanding Breathalyzers: How They Work & BAC Estimation

A breathalyzer is a device used to estimate a person's blood alcohol concentration (BAC). It works by measuring the amount of alcohol on a person's breath. Only a blood sample analysis can give a direct measure of BAC, and the breathalyzer was developed because a blood sample analysis isn't always practical. A breathalyzer's most common use is by law enforcement officers at the side of a road to give an immediate indication of whether or not a driver is under the influence of alcohol.

Instructions

• 1

  Press a personal breathalyzer's power button until the display turns on and the unit beeps.

• 2

  Wait about 10 seconds for the unit to warm up while the "Wait" symbol or green light flashes. When the breathalyzer is ready for use, the "Wait" symbol goes away or the green light stops flashing and remains lit.

  If the unit takes longer to warm up, press its power button repeatedly to clear the sensor.

• 3

  Blow into the breathalyzer for about five seconds. The device must be near your mouth.

• 4

  Check the device's front display for results when you hear a beep. A green light indicates a BAC of less than 0.02 percent. A yellow light indicates the BAC is from 0.02 to 0.05 percent. When both lights are lit, the BAC is above 0.05 percent. Disregard results that show a red light, which indicates the unit has a fault.