How Breathalyzers Work

With so much of your Ohio DUI criminal case resting on the results of your breath test, you are probably curious about how these machines work. Columbus DUI lawyer Peter Binning has taken extensive training about all aspects of defending DUI cases, including the function of the breathalyzer. Now, he wants to share this information with you.

The government uses two main types of breathalyzer to measure your blood alcohol concentration (BAC), the fuel cell breathalyzer and the infrared breathalyzer. The infrared breathalyzer is the most common, and will be discussed below. But before we can discuss how the machine makes its calculations, you have to understand what is being measured.

What Breathalyzers Measure

When you take the Ohio breath test, the officer will instruct you to blow out as hard as you can for a prolonged amount of time in order access the air from the deepest part of your lungs. This air, known as alveolar air, contains the highest concentration of blood vessels. Because alcohol molecules can pass through cell walls very easily, it is believed that your alveolar air most closely matches your BAC.

How Breathalyzers Work Internally

When you blow into the breathalyzer, your alveolar air passes through several different wavelengths of infrared light. This light then passes through a filter wheel, which is supposed to only allow alcohol molecules to pass through. This light is then converted to an electrical impulse, which is calculated by the computer into your BAC reading.

One of the main ways this test can go wrong, is that ethyl alcohol—the substance tested by the machine—is very similar to many other chemical compounds. The government will tell you that the filter wheel knows the difference between ethyl alcohol and other substances, but empirical tests have proven that this is simply untrue. Thus, the machine may be registering an innocent molecule as alcohol and showing that you are drunk when you’re not.

Ultimately, breathalyzers are machines run by a computer code, and computers can only calculate what they are told you. The breathalyzer does not take your unique physical make-up into account when it runs its calculations. For example, it assumes you will have a 2100:1 ratio of blood alcohol to breath alcohol. It also makes assumptions about your gender, body temperature, lung capacity, and more. If any one of these assumptions is incorrect (and they probably are) you will not receive an accurate reading.

We hope this page has been informative on the function of the breathalyzer machine. However, if you have been arrested with an Ohio DUI after taking the breath test, we want you to call our offices today! Columbus DUI lawyer Peter Binning has the knowledge and experience necessary to build a defense and fight your criminal charges in court.