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Understanding breath tests and the factors that skew the results

On Behalf of | Jan 1, 2024 | DUI

A breath test, commonly referred to as a Breathalyzer, is widely used by law enforcement officials to detect the presence of alcohol on a driver.

Many people are familiar with breath tests and understand that when a person is pulled over for suspected drunk driving, he or she may be asked to breath into a breath device that will reveal whether he or she have been drinking and is over the legal alcohol driving limit.

But, aside from the basic principle, many people don’t quite know how it works. How exactly can a simple device determine who many beers a person has had?

Understand how a breath test works

When an individual takes a sip of alcohol, that alcohol is immediately absorbed into the capillaries of the mouth, esophagus, stomach and intestines where it enters the bloodstream.

The blood containing the alcohol moves throughout the body. As it flows through the lungs, it comes into contact with the air breathed in. The alcohol in the blood essentially attaches to the air and then breathed out.

Essentially, that breath of air that contains a concentration of alcohol is the same as the concentration in that person’s blood-hence the phrase “blood alcohol concentration” or BAC.

However, this basic premise isn’t black and white and many factors can contribute to the breath test device calculation.

Factors that play a part in a breath test reading

  • Cell volume of the blood: This principle is a bit tricky to comprehend. However, it means that a person who has a lower cell volume will likely have a higher BAC reading. Cell volume refers to the makeup of the cells in a person’s blood. Tissue, liquid and red and white cells all make up a person’s blood. Depending on how much tissue or liquid is contained in the cells will determine the BAC outcome.
  • Body temperature: The breath test reading is based on a typical 98.6 degree human body temperature. But if a person has a higher body temp, the BAC reading could be higher. It’s estimated that just 1 degree higher difference raises the BAC value 7 percent. This is problematic for those who have been outdoors for long periods during summer months, or suffer from a cold during winter months.
  • Presence of Methyl compounds: The presence of methyl compounds like ketones in the breath can raise the BAC limit as well. This is problematic for diabetics or individuals ingesting dietary supplements.
  • Outside air temperatures: Breath tests are typically calibrated to operate under preferably warm temperatures. However, if an officer pulls over a vehicle in the winter and takes the breath test outside to the suspected driver, the device isn’t given adequate time to adjust to the drop in the outside temperature. This could lead to an incorrect BAC reading.

Other factors such as consuming an alcoholic drink recently after getting pulled over, or the presence of vomit, blood or acid reflux within a person’s mouth can also affect the accuracy of a breath test.

Despite the suspected nature of these devices, they are still used by officers and their results as evidence in a court of law. Those who have taken a breath test are encouraged to consult with an experienced DUI attorney as soon as possible. A lawyer can investigate the authenticity of the test given.