How Is Breath Testing Done?

Police breath alcohol concentration testing in Texas is done by a machine named an Intoxilyzer 5000. Breathalyzers are not used.

The Intoxilyzer machine, which costs approximately $7,500.00, is said to work on the basis of infrared light absorption by alcohol detected in a person's breath. According to its manufacturer and the Texas Department of Public Safety (DPS), which certifies and writes the rules for its use, the machine determines alcohol concentration by subtracting the amount of light absorbed from the person's breath sample and then compares that amount to the amount of light originally introduced into the breath sample -- the difference is the test result.