Texas DWI breath test information

There are three major types of breath testing devices, and each is based on a different principle.Breathalyzer - Uses a chemical reaction involving alcohol that produces a color change
Intoxilyzer - Detects alcohol by infrared (IR) spectroscopy

Alcosensor III or IV - Detects a chemical reaction of alcohol in a fuel cell

Regardless of the breath test type, each device has a mouthpiece, a tube through which the suspect blows air, and a sample chamber where the air goes. The rest of the device varies with the type.

Breathalyzer
To measure alcohol, a suspect breathes into the device. The breath sample is bubbled in one vial through a mixture of sulfuric acid, potassium dichromate, silver nitrate and water. The principle of the measurement is based on a chemical reaction created by interaction between the breath tests and the substances listed.

Intoxilyzer
This device uses infrared spectroscopy, which identifies molecules based on the way they absorb infrared light. As a breath analyzer, the intoxilyzer calculates the BAC based on the absorption of infrared light.

Alcosensor III
or IVModern fuel-cell technology (which may power our cars and even our houses some day) has been applied to breath alcohol detectors. Devices like the Alcosensor III and IV use fuel cells. Police officers can carry portable breath testing devices (like the Alcosensor) that use the same principle as full-size devices. Court cases can turn on the Intoxilyzer 5000 Weaknesses, however, so prosecutors rely on the results obtained from full-size devices.