Attorney at Law


James Parker
February 16, 2022
Last reviewed by
August 17, 2023

What Is a Breathalyzer?

A breathalyzer is a small, compact device that is designed to detect alcohol on the breath of the user. Breathalyzers analyze the alcohol content of the breath of the user and use that information to determine the amount of alcohol in the user’s bloodstream. 

This type of device is used chiefly by police to determine how intoxicated a driver may be, but breathalyzers are also employed by substance abuse centers, businesses, and as part of ignition interlock devices. In general, there are two types of breathalyzers on the market: semiconductor breathalyzers and fuel cell breathalyzers. 

Breathalyzers have traditionally used semiconductors in detecting alcohol. This relatively inexpensive device uses a tin-oxide semiconductor to convert the ethanol on the breath of the user into acetaldehyde. These devices are now regarded as inexpensive and effective for low-volume testing but not as accurate. The semiconductors have been known to react with other bodily chemicals such as ketones or foreign agents like tobacco smoke.

The newer style of breathalyzer, the platinum fuel cell breathalyzer is considered to be the higher-end, more sensitive, and more accurate breathalyzer. By utilizing a more sensitive metal, the fuel cell breathalyzer is designed to give fewer false-positive readings. 

Key Takeaways

  • A breathalyzer is a compact device that is designed to measure how much alcohol is in a person’s body
  • Breathalyzers are the most common tool used by law enforcement officials who suspect someone of driving under the influence of alcohol
  • Breathalyzers are not perfect and can be influenced by chemicals and substances that are not alcoholic
  • If you have been charged with a DUI on the strength of a breathalyzer result, an experienced DUI attorney may be able to improve the outcome of your case by leveraging experience and expert testimony.

Breathalyzers and Driving Under the Influence (DUI) Charges

Breathalyzers play a controversial role in the space of DUI charges. While they are the most commonly administered test to arrest and charge an individual with a DUI, they are not infallible. There are a number of factors that can influence the readings that a breathalyzer returns. These include: calibration, environment, foreign contaminants, human error, precision errors, and software malfunctions. 

Breathalyzers must be regularly calibrated and their batteries must be replaced periodically in order to ensure accuracy in their readings. A miscalibrated breathalyzer will not return accurate results and may result in a wrongful conviction. Even a correctly calibrated breathalyzer can be off by as much as 1%. This means that an individual who is judged to be at exactly the legal limit (8% alcohol by volume) may in fact be below the limit and just be the victim of the breathalyzer’s margin of error.

In addition to calibration errors, there are environmental and contamination factors that can skew a breathalyzer’s accuracy. If the user has consumed alcohol, suffered from acid reflux, or vomited shortly before the administration of the test, then the breathalyzer may read the alcohol directly present in the mouth rather than the alcohol on the breath and return a significantly higher reading. If the air contains particles of varnish, plastics, adhesives, or paint fumes, these chemicals may also throw off the breathalyzer reading in addition to posing a health hazard for all involved.

Breathalyzer tests are also not able to administer themselves. An error in the user or administrator of the breathalyzer test can result in the results being thrown into question. The most precise measurement of intoxication requires several readings to be taken a few minutes apart while also accounting for factors previously mentioned. If the person administering the test is impatient or misinformed, they may make their judgement based on one or two results. 

The final complicating factor in getting an accurate breathalyzer reading is the device itself. In addition to the physical errors that can occur with the measuring device itself, a breathalyzer can also suffer from a software error. A simple glitch or hiccup in the code can result in an erroneous reading. If a breathalyzer’s software is corrupted or malfunctioning, this can be hard to notice at the moment and may not be detected until much later. 

On top of all of these potential misreadings, a breathalyzer does not even return the user’s blood alcohol content (BAC). Instead, the device returns the user’s breath alcohol level, which must then be converted into an estimation of BAC. Some states, such as Texas, have passed laws limiting the breath alcohol level in addition to the blood alcohol level, but the issue is still regularly brought into court. For these reasons, even though it can be the basis for arrest or further inquiry, the results of a breathalyzer test are not admissible in court.

Bottom Line

Breathalyzers are a ubiquitous tool of law enforcement officials and their confidence in these devices can rub off on a jury should it go to trial. However, this confidence can be misplaced and breathalyzers can be inaccurate in large and small ways. The best way to demonstrate the errors in these readings is to retain an experienced DUI attorney.

An experienced DUI attorney can use expert testimony and cross examination to expose the errors in the administration and interpretation of the breathalyzer tests. An experienced DUI attorney can help convince the jury and get you the best possible outcome for your case.

Ask a Lawyer

Ask your own question and get advice from expert attorneys
Ask Question

Featured DUI Law Lawyers

D&O Law Group, LLC

15 years in practice
Criminal Defense, Divorce & Family Law, DUI Law, Personal Injury
View Profile

VanEngen Law Office, P.C.

6 years in practice
Auto Accidents, DUI Law, Personal Injury
View Profile

The Wright Legal Group, LLC

13 years in practice
Auto Accidents, DUI Law, Personal Injury, Premises Liability
View Profile

D&O Law Group, LLC

15 years in practice
Criminal Defense, Divorce & Family Law, DUI Law, Personal Injury
View Profile

Law Offices of Ricardo J. Mauro, P.C.

29 years in practice
Auto Accidents, Personal Injury
View Profile

Law Offices of Robert F. Julian

47 years in practice
Auto Accidents, Construction Injury, Personal Injury, Wrongful Death
View Profile


Are you looking for an attorney? Do you have questions about a legal case you are facing? Contact us now and we will put you in touch with a lawyer for free.
Attorney At Law is changing how clients connect with lawyers. By providing an innovative platform to lawyers who want to expand their practice’s reach, AAL is bringing law practices into the future.
6142 Innovation Way
Carlsbad, California 92009
Some of the content of this website may be considered attorney advertising under the rules of certain jurisdictions. The information on this website is for general information purposes only. Nothing on this site should be taken as legal advice for any individual case or situation. This information is not intended to create, and receipt or viewing does not constitute an attorney-client relationship.
crossmenuchevron-upchevron-down linkedin facebook pinterest youtube rss twitter instagram facebook-blank rss-blank linkedin-blank pinterest youtube twitter instagram