What Is A Breath Alcohol Test & How Does It Work


A breath alcohol test is a quick and easy way to find out if you have been drinking or not. There are two types of breath alcohol tests:

  • Breathalyzer – a device that measures your blood alcohol content (BAC) by testing your breath.
  • Field sobriety test – a series of physical tasks that are performed on the side of the road by the officer in order to determine if you are too drunk to drive.

How a Breath Alcohol Test Works

Most people are familiar with breathalyzers, which use infrared light to measure the amount of alcohol in the breath. A breath alcohol tester works on the same principle but uses a different technology: fuel cells.

The fuel cell, also known as an electrochemical cell, consists of two electrodes separated by an electrolyte that conducts electricity. When you breathe into the device, a current flows between the electrodes as you exhale. The amount of current depends on how much alcohol is present in your breath. The higher the concentration of alcohol, the greater the flow of electricity will be between the electrodes (and vice versa).

Breathalyzers come in various forms: some fit into your car’s ignition switch so they can be used any time; others are handheld devices that you blow into after you’ve been pulled over for suspicion of driving under the influence (DUI). Other types resemble flashlights and can be used at roadside stops when police suspect someone might have been drinking too much to drive safely.

Who Administers Breath Alcohol Tests?

Breath alcohol tests are administered by law enforcement officers or by a person with the proper training. The officer may use a hand-held breath alcohol tester, which is similar to a Breathalyzer, or he or she may administer the test at the police station. If you refuse to take this test, the results will be used against you in court.

The results of a breath alcohol test are usually admissible in court as evidence against you if they are taken within three hours of your arrest and show that your blood alcohol content (BAC) was .08 percent or higher. A breath sample could be used as evidence only if it was taken within two hours of driving.

A urine test for drugs may be used if there is reason to believe that you have been using illegal drugs while driving. A urine test can detect many common illegal drugs, including marijuana and cocaine. The urine test detects only recent drug use; traces of most drugs do not remain in urine after four days.

How Do You Get Tested?

Testing usually takes place on the spot, with police officers administering the test after pulling you over for suspected drunk driving. However, some states allow police officers to administer a breathalyzer test at any time during an investigation into drunk driving; this gives them an opportunity to collect evidence before taking you back to the station house for further questioning and testing if necessary.

How Accurate Is A Breath Alcohol Test?

The answer to this question is not as simple as it might seem. The accuracy of these devices has been questioned, but they are generally considered reliable for measuring blood alcohol content (BAC). In fact, there are several factors that affect the accuracy of a breath alcohol test:

  • The type of breathalyzer used
  • The person who is taking the test
  • The type of sample being tested
  • The environment in which the test is conducted
  • Let’s take a closer look at each factor.
  • How long since you last ate or drank anything
  • How well do you follow instructions when taking the test

What Happens If You Fail Test?

If you fail a breath alcohol test, or if your blood alcohol concentration (BAC) is above the legal limit of 0.08%, then you could be charged with drunk driving. In addition to facing criminal penalties, you also face penalties from your employer for violating company policies on alcohol use.


For those considering a driver’s license suspension due to a DUI, understanding the basics of a breath alcohol test is essential. After all, breath testing can determine whether or not your suspension will be temporary or permanent. It also affects your ability to apply for an ignition interlock permit. As such, it’s important to understand what you can and cannot do during the test.