Breath Test machines used in DWI cases and DWI arrests can vary. Many companies make and sell breath test machines. While Breathalyzer was one of the first, other companies like Intoximeter have created many versions of a breath tests, including four models of the Alco-Sensor DWI breath test devices. Police stations and counties differ as to which DWI device is used, however almost all of the handheld DWI breath test devices work in a similar way.
When alcohol is consumed, it takes a little while for the alcohol to be absorbed by the body, which is when the effects of alcohol, in a DWI sense, are felt. In other words, five minutes after drinking a shot of vodka, a person will not feel any effects, however thirty minutes later, they will. During those thirty minutes, the alcohol from the drink is digested, moving into the blood stream and to the lungs, where some of the alcohol crosses the alveoli, or membranes of the lung's air pockets. Since alcohol is volatile, meaning that it will evaporate, the air around the alveolar accumulates evaporated alcohol, and that alveolar air has a direct relationship to the concentration of alcohol in the blood; at a ratio of 2,100 : 1. When an intoxicated individual exhales, out comes the alveolar air, which can be detected and converted by a breath machine to measure blood alcohol concentration.
Out of the major brands of DWI alcohol detection devices, breath alcohol is measured as follows:
The Breathalyzer uses a blow tube to take a sample of a DWI suspect's breath, which bubbles through a small tube of sulfuric acid, potassium dichromate, silver nitrate, and water. Then, an array of photo cells measure any color change of the testing tubes, using a meter to determine which chemical color corresponds to a given BAC.
The Intoxilyzer uses a lamp to generate a multiple wavelength infa-red beam that passes though a sample chamber, where the beam is then focused by a lens onto a spinning filter. The filter is made of smaller narrow filters that are spaced specifically for wavelength bonds in ethanol. Any light passing through the smaller narrow filters is detected and converted into an electrical pulse. Lastly, that pulse is relayed to the microprocessor, which uses the pulses to determine the blood alcohol concentration.
For the Alcosensor III and IV, DWI breath devices use fuel cells, which has two platinum electrodes with an acid electrolyte substance placed in the middle. When breath is blown by a DWI suspect into the fuel cell, it travels through one side of the cell itself, allowing the platinum to oxidize any alcohol, thereby producing acetic acid, protons & electrons. Electrons travel along a wire from the platinum electrode, and is attached to a current meter, continuing to the other side of the fuel cell. Protons go along the lower portion of the cell, combing with oxygen and any electrons from the opposite end of the cell to produce H2o. The greater the amount of alcohol oxidized, the larger the electrical current. Lastly, a processor within the DWI breath device measures that current and calculates blood alcohol concentration levels.