What is the Intoxilyzer 8000 (Breathalyzer)?

The Intoxilyzer 8000 is the instrument Oregon law enforcement uses to estimate the blood alcohol content (BAC) of suspected DUI drivers. The Intoxilyzer 8000 requires a person to blow into a tube connected to the machine so the machine can approximate the blood alcohol content of the individual.

Factors That Influence Breathalyzer Results

The machine assumes a "partition" ratio of 2,100:1, or, that for every molecule of alcohol in your breath, there are 2,100 particles in your bloodstream. This partition ratio is based upon assumptions that, may in theory be a fair estimation of the population as a whole, but can vary widely based upon the individual. Depending on the person’s size, absorption/dissipation ratio, how much he or she has eaten, and a number of other factors, the partition ratio could be much less or more than the assumed 2,100:1.

The Intozilyzer 8000 also is vulnerable to several other issues. Studies have revealed that radio frequency interferences (RFI) can occur through instruments such as police radios that may be near the Intoxilyzer. Thus, it is imperative that no radio devices be near the machine when it is in operation. The Intoxilyzer is supposed to detect RFI and abort the test and print out a result showing “RFI” if it detects the interference.

The Impact of Mouth Alcohol 

Mouth alcohol (residual alcohol in the mouth) also can affect the approximation of the machine. The Intoxilyzer has a “slope detector” or “mouth alcohol detector” that is supposed to pick up on mouth alcohol and abort the testing sequence. Unfortunately, the slope detector does not always work and an inaccurate result can be displayed due to residual alcohol or other substances. This is the reason the operator of the machine is required to observe the test subject for 15 minutes to make sure the subject does not consume anything, burp, vomit, or regurgitate.

In a study conducted by several scientists, the presence of alcohol in the mouth from gargling mouthwash could suggest a high BAC when the person had not actually consumed any alcohol. Additionally, mouthwash that had been swallowed led to an inaccurate result when the sample was taken 5 or even 10 minutes after consumption. Alcohol does not absorb into the system immediately but rather takes some time to get into the bloodstream.

Breathalyzer Testing Protocol

The presence of outside alcohol also can affect a BAC result. The testing sequence for the Intoxilyzer 8000 requires the operator to conduct a few “air blanks” in order to ensure outside alcohol does not influence the machine’s result. The machine also is required to run a diagnostic test of a known control to check the accuracy of the machine.

The testing sequence also requires two samples from the subject. The machine then will determine if the samples are within a set range (within 10% of the mean value of the two samples) in order to produce an assumed accurate result. If the samples are not within that range, the test will be aborted.

Thus, while the Intoxilyzer 8000 will provide an approximation of a person’s blood alcohol content, it is not infallible. There are a number of issues and factors that can affect the machine’s estimation. The individual subject and his or her rates of absorption and dissipation, as well as pattern of drinking, also can affect the result the machine produces. Depending upon the Intoxilyzer alone to determine a person’s intoxication and ability to safely operate a motor vehicle is highly suspect.

Rob Crow
Connect with me
Licensed to practice law in all State & Federal Courts in Oregon.
Post A Comment