How Breathalyzers Work

If you have ever been arrested for an Illinois DUI you have probably wondered how breathalyzers work. Illinois DUI Attorney Brian Roberts has taken extensive training on various aspects of defending people charged with an IL DUI. This page will give you a general understanding of how a DUI breath machine works.

There are two main types of breathalyzer machines. Breath testing machines will typically use either infrared light or fuel cells to measure your blood alcohol content. Each of these are explained more fully below, but first you need to know what is being measured by the machines.

What Breathalyzers Measure

Illinois DUI breath machines are supposed to measure air from the deepest portion of your lungs. This alveolar lung air is that air that interacts with your blood vessels and carries carbon dioxide from your blood while also carrying oxygen to your blood. The concentration of alcohol from this region of your body is believed to be aligned with the concentration of alcohol in your blood.

How Breathalyzers Work Internally

It is important to remember that breathalyzers are machines that run off a computer program. They measure only what their computer program tells them to measure. Thus, the breathalyzers assume certain things about everyone who takes a test. They assume that everyone who takes the test will have a 2100:1 ratio of breath alcohol to blood alcohol. They also assume certain things, like your gender, your lung capacity, your body temperature and much more.

The most common breath machines in Illinois use infrared technology to measure your blood alcohol concentration. For that reason, that is the technology discussed here.

When you blow into an infrared breathalyzer your breath travels past a lamp that generates multiple wavelengths of infrared light. This light passes through a chamber and is directed to a filter wheel. The filter wheel is set up to only allow the chemical compounds that create alcohol pass through the wheel. As the light passes through these filters the light is measured by a photocell that converts it into an electrical impulse. That impulse is then sent to a computer microprocessor that calculates how much light passed through the filter and converts it into a specific BAC number.

There are a lot of problems with the way this process actually works including, similarities between the chemical composition of ethyl alcohol and other chemicals. Although the government claims the filter on these machines can tell the difference between these chemicals, experience and science has proven time and again that they cannot consistently tell the difference.

If you only read this page because you were curious in how breathalyzers work then I hope it has been informative. If you have been arrested for an Illinois DUI then call the Illinois DUI attorneys at our office right now for immediate help.