About Us

Proctorcars is a brand new car magazine bringing you the latest information about car technology, in-depth guides on a variety of automotive and driving topics as well as fun and interesting articles that you don’t want to miss!
Read More

How do Alcohol Breathalyzers Work and How Accurate Are They?

Image courtesy of KOMUnews on Flickr, hosted under CC BY 2.0.

Police departments and sheriff’s offices most commonly use breathalyzers to check whether a driver was drinking any alcoholic beverages and how much alcohol they have had. The law requires that the breathalyzers used by the police force meet certain standards. However, as there are several breathalyzer varieties on the market, some of them are also available to the public for personal use. Let’s see what kind of breathalyzers there are and how they work.

What Is a Breathalyzer?

A breathalyzer is a device that is used to estimate a person’s blood alcohol concentration (most often referred to as BAC) by using a sample of their breath. The first breath alcohol tests were developed for the police in the 1940s, but Professor Robert F. Borkenstein of the Indiana State Police created the modern device in 1954. Although the brand name Breathalyzer is a registered trademark, the term “breathalyzer” is used as a generic term for all breath test devices.

How Can a Breathalyzer Determine Your BAC?

Image courtesy of West Midlands Police on Flickr, hosted under CC BY-SA 2.0.
Image courtesy of West Midlands Police on Flickr, hosted under CC BY-SA 2.0.

When you drink alcohol, it circulates in your blood and reaches the lungs. Similar to how carbon dioxide diffuses out of your blood, the alcohol diffuses as well. When you breathe, you exhale the alcohol. A breathalyzer can measure how much alcohol is present in your breath and provide an estimate of your BAC. The breath-to-blood alcohol ratio is 2,100:1, which assumes that there are 2,100 milliliters of alcohol in your blood for every 1 milliliter of alcohol in your breath.

In the United States, it’s illegal to drive with a BAC of .08 percent or higher, at which point it’s considered a DUI or DWI. However, the margin of error with portable breathalyzers can reach 15 percent, and up to 23 percent of the drivers charged for DUI/DWI may be victims of inaccurate breathalyzer results. The most accurate way to test BAC is by sampling blood. All other tests have a higher margin of error. This doesn’t mean that you can dispute your results if you’ve had a few, however.

Types of Devices

Image courtesy of Oregon Department of Transportation on Flickr, hosted under CC BY 2.0.
Image courtesy of Oregon Department of Transportation on Flickr, hosted under CC BY 2.0.

There are numerous types of breathalyzer devices, but all of them consist of a mouthpiece, a tube that you blow into, and sample chambers where your breath is tested. From this point, a variety of technologies are used to produce a reading. Devices that use fuel-cell technology generally cost more but are more accurate, while infrared devices cost less.

Fuel-Cell Breathalyzers – used in devices like Alco-Sensor III or IV, fuel-cell technology helps determine BAC by how strong of an electrical current is produced. The sample chamber consists of two platinum electrodes and a porous acid layer in between. When air containing alcohol passes through, the electrodes oxidize any alcohol and produce acetic acid, electrons and protons. The electrons will flow through a wire from the platinum electrode to the other electrode. When they do so, they move through an electrical current meter. The more energy that passes through the electric pathways, the higher the BAC result. Fuel-cell breathalyzers are the most accurate among all breath test devices, and are the only type of devices that the law allows authorities to admit as evidence in court.

Infrared Breathalyzers – often called intoxilyzers, these devices use the infrared spectrum to detect intoxication by identifying molecules based on how they absorb IR light. In the sample chamber, an internal lamp produces a broadband infrared beam that passes through the exhaled breath and through a filter wheel. Since different types of molecules absorb different amounts of lights, the filter can determine how much ethanol is present by identifying its wavelengths and the amount of light that was absorbed.

Color-Changing Breathalyzers – A color-changing device uses a mixture of chemicals that react with alcohol and produce a color that indicates the BAC. It has two vials of liquid. Your breath passes through the first one when you breathe into the device. Sulfuric acid in the breathalyzer removes the alcohol from your breath and sends it into a liquid solution, where the alcohol reacts with other chemicals. The resulting color change is compared with the unaltered chemicals in the second vial. The higher the degree of color change, the higher the BAC.

Breathalyzer Gadgets and Apps 

Photo by Monolithicfungus on Wikimedia Commons / CC BY-SA 4.0.
Photo by Monolithicfungus on Wikimedia Commons / CC BY-SA 4.0.

Along with these three main types of breathalyzers, several companies make devices for personal and professional use. Many of them come with corresponding apps that work on your smartphone, but some feature a screen that shows you the results.

BACtrack – KHN Solutions Inc. launched a line of BACtrack breathalyzers. The BACtrack Vio and BACtrack Mobile Pro both feature fuel-cell technology and Bluetooth technology to synchronize and track your results with the corresponding smartphone app. They also feature ZeroLine Technology, which provides an estimate on when you will become sober again.

Breathometer and Breeze – Breathometer, Inc. makes the Original Breathometer, which uses advanced semiconductor technology and connects to your smartphone through the headphone jack. Its Breeze device uses fuel-cell technology and Bluetooth. The Breathometer smartphone app features Back to Zero to estimate when you will be sober and has a Get Home Safe button that will call a taxi or Uber for a ride home or to a restaurant. You can use it to test friends as well.

AlcohootAlcohoot is a device from Vertisense Inc. that uses fuel-cell technology and plugs into the headphone jack on your smartphone. It comes with changeable mouthpieces for improved accuracy when more people use the same device. The Alcohoot app can call a taxi or other car service for a ride home.

Factors That Affect Breathalyzer Accuracy

Since breathalyzers do not physically measure BAC and only provide an estimate, several factors can lower the accuracy of results and make them lower or higher.

One factor that people cannot control is having a higher body temperature, which makes the breathalyzer result higher because of higher volatility. Differences in blood composition may cause higher readings as well. Lower readings could occur when the test is taken before the alcohol is fully absorbed into the blood, which takes one to two hours after drinking.

Electrical interference from police radios and smartphones is another possible factor that results in lower accuracy. Additionally, some breathalyzers are unable to tell the difference between alcohol and other simple chemical compounds that are present in the breath or vicinity of the test. Methyl compounds, for example, are present in vinegar, paint remover, cleaning fluids and the breath of people suffering from diabetes. More factors that can cause higher readings include acid reflux, blood or vomit in the mouth, breath freshener or mouthwash, or alcohol residue in the mouth.

How to Test Your BAC Accurately

Pixabay.com / <a href="https://creativecommons.org/publicdomain/zero/1.0/" target="_blank">CC0 1.0</a>.
Pixabay.com / CC0 1.0.

Although there are many factors that make breathalyzer results inaccurate, there are a few ways that you can improve the accuracy. After having an alcoholic drink or a cigarette, wait at least 20 minutes before you test your breath. Only use the breathalyzer when your body temperature is in the normal range. Breathe normally before taking the test because hyperventilation and hypoventilation can affect the result.

Photo by Oregon Department of Transportation on Flickr / CC BY 2.0.
Photo by Oregon Department of Transportation on Flickr / CC BY 2.0

During the test, blow into the mouthpiece with a slow and steady breath. Don’t stop until the device gives you the signal. For consistent results, make the force of your breath the same every time you use the breathalyzer. While the device is analyzing your breath, which can take several seconds, don’t push any buttons. After every 200 to 300 uses, calibrate the breathalyzer to maintain accuracy, which may need to be completed by the manufacturer.


While authorities primarily use breathalyzers to make sure people are not driving under the influence, you can use one of the many personal devices available on the market to ensure the safety of yourself and those around you. Having a device that will call you a taxi at the push of a button is really convenient, don’t you think?

Have you tried any of the breathalyzers listed above?

 Do you have any of the mentioned apps installed on your phone?

 If so, how was your experience?