How Does a Breathalyzer Work?

How do you know when you’ve had a little too much to drive? The legal blood alcohol limit in most states is 0.08, but what does that mean? A beer? Two? Honestly - it really depends. Everyone metabolizes alcohol at different rates and it’s impossible to say just how many is too many. The only reliable way to decide if you’re OK to drive home or not is to test your blood alcohol level before the police do it for you! And the only way to easily do that is with a breathalyzer test.

So how do breathalyzers actually work?

Alcohol is not really digested like food or other drinks. It is actually absorbed into the membranes in your mouth, throat and intestines into the bloodstream. When the blood passes into the lungs, the alcohol is expelled through the breath. This is what allows the breathalyzer to measure the level of alcohol in the breath and is then translated into the level in the blood. The ratio of alcohol in the breath to alcohol in the blood is 2100:1. This is how the breathalyzer can accurately measure the levels based on the legal limit.

No matter what kind of breathalyzer you’re using, whether it is a disposable one-use one, a sophisticated personal use device, or a professional breathalyzer like the police use, they all work on the same basic principles. You blow into a tube and the air goes into a chamber that contains two cylinders that contain the chemicals for testing. One cylinder receives the breath and the other remains untouched. The solution in the cylinders is made up of water, potassium dichromate, sulphuric acid and silver nitrate. A chemical reaction occurs when the alcohol is introduced to the chemical solution which causes the solution to change color. Then, an electric current measures the difference in the two vials – the pure one that the one that contains the alcohol. The degree of difference determines how high the blood alcohol content is.

Since there are slight variables when testing BAC (Blood Alcohol Content) using a breathalyzer, it cannot be 100% accurate all of the time, though it is very close. So it is advisable to err on the side of caution when it comes to deciding if you’re safe to drive. Always wait 20 minutes after drinking to take the breathalyzer test, and if the reading is close to the limit, wait a while just to be safe.