HOW BREATH TESTING IS DONE WITH THE INTOXILYZER 5000

The State of Texas uses a machine called the Intoxilyzer 5000, which is commonly referred to as a  "breathalyzer."

The Intoxilyzer 5000 costs about $7,500.  There are several models of the Intoxilyzer 5000 in use in Texas including the model 64, 66, 68 and 68-EN.  Many of these earlier models have been in service for 15 or more years.

The Intoxilyzer 5000 is simply a computer based on very old technology.  The brains of this outfit is a Z-80 microprocessor which was introduced almost 30 years ago in 1975.  The Z-80 microprocessor was the basis for some of the very first home computers in the early 1980's.  Remember the "Radio Shack" TRS-80.

The Intoxilyzer 5000 works on the theory of infrared absorption. The machine has a light bulb positioned at one end of a breath capture cylinder. There are filter wheels at the other end of the cylinder and on the other side of these filter wheels is a light receiver.

A person suspected of or under arrest for DWI will blow into a breath tube which leads to a breath chamber cylinder. The machine shines a light through this cylinder and the filter wheels will be spinning on the other end of the breath tube chamber.  The infrared light causes the alcohol molecules to "vibrate" or "absorb" light at a particular frequency. The filter wheels are designed to filter out potential contaminants.

The amount of the breath sample and any reading of alcohol are very minute. The machine must make a multiplication conversion to an amount great enough for us to understand. The difference in light emitted and received is computed through a computer program in the machine to come up a value that can be compared to a .08.  The conversion the machine makes on the differences in light would be the equivalent of taking the paper towel tube and increasing its size to that of a 55 gallon drum! Any error would then be exaggerated by that amount.

HOW RELIABLE IS THE BREATH TEST?

There is much debate on the Intoxilyzer 5000. Proponents of it state that the machine will only read light absorbed by alcohol, while opponents state the machine often misreads as alcohol other commonly found substances in the breath, thus giving an inaccurate high reading.

Texas law only requires that the Intoxilyzer 5000 perform within a plus or minus 10% accuracy rate. This means that a 20% variance in "ok for government work".  When the machine is periodically checked for proper function and accuracy and known value of alcohol solution -- 0.080 -- is used to test the machine, if the results are within 0.072 and 0.088 the machine is deemed to be working properly.

An everyday example is if you are stopped and arrested for DWI and take a breath test, and you blow a 0.080, when your actual alcohol content is something less, you still face the additional charge of driving with a .08 or higher. Very Scary.

The manufacturer does not warrant the Intoxilyzer 5000 for any particular purpose.The machine is not warranted for accurate and reliable breath testing.

The Intoxilyzer also assumes that everyone tested will have a blood/breath ration of 2100/1 (i.e. 2100 parts of alcohol in the breath for every 1 part of alcohol in the blood). If a person has a higher blood/breath ratio (i.e. 2400/1) the test will not be adversely affected by this assumption. However a person with a lower blood/breath ratio will be adversely affected because the Intoxilyzer will erroneously read too high, thus a person who should test at .05 or .06 could actually test well above a .08  Additionally, scientists have documented people with blood/breath ratios as low as 1100/1.

A person with a fever will have a higher breath test reading than an identical person without a fever. Therefore, the temperature of your body can affect what the Intoxilyzer reads, and your body temperature has nothing to do with the amount of alcohol you may have or have not consumed.