Maine’s Premier DUI
& Criminal Defense Law Firm


The Three Different Models of Breath Testing Machines

Posted by William Bly | Dec 26, 2017 | 0 Comments

In a recent blog post, we explained how – technically speaking – there's no such thing as a “breathalyzer.” Instead, the word “breathalyzer” is a brand name for some of the chemical breath testing machines on the market, much like a Kleenex is a brand name for some of the facial tissues you can buy. In fact, there are scores of “breathalyzers” that have been approved for police use by the National Highway Traffic Safety Administration (NHTSA), like the Lifeloc Technologies Phoenix 6.0BT, the Lion Laboratories Intoxilyzer 200D, or the Intoxiimeter 3000 DFC.

While there are plenty of possible breath testing kits to choose from, however, they all fall into one of the three following categories, based on how they work:

  1. Breathalyzers, which uses chemicals that change colors when they interact with alcohol,
  2. Intoxilyzers, which detect alcohol through infrared spectroscopy, and
  3. Alcosensors, which uses a fuel cell's chemical reaction to alcohol.

Breathalyzer Models: Using Color Changes to Detect Alcohol

The original Breathalyzer, one of the earliest chemical breath testing kits, invented in 1953, used the color changes from a specific chemical reaction to determine the alcohol content of an air sample. Many current breath testing kits are based on this system, as well.

The chemical process that these models use is a color change in potassium dichromate. Alone, this chemical is reddish-orange. When it is mixed with alcohol, it turns green.

Models based on the original Breathalyzer keep two vials of potassium dichromate inside them. One reacts with a breath sample, while the other stays pure. A photocell system then compares the difference in color between the two, and its reading is interpreted as a blood alcohol content (BAC).

Intoxilyzer Models: Detecting Alcohol With Infrared Light

In an Intoxilyzer model, a breath sample is held inside the machine while infrared light is shined from a lamp at the sample. Because all different chemicals absorb light at different wavelengths, if the wavelength that corresponds to alcohol doesn't make it through the breath sample, it means there's alcohol in it. The more alcohol in the breath sample, the more that particular wavelength of light gets absorbed, the less light passes through to the sensor on the side of the machine opposite the lamp.

Alcosensors: Alcohol Powers Batteries

Modern alcosensor breath testing machines are like fuel-cell batteries, with platinum electrodes on the ends and a porous acid-electrolyte cell fixed between them. Any alcohol in a breath sample gets oxidized and broken apart by the electrode on one side, to reattach together as water, on the other side of the battery. This process produces an electrical current, which gets measured and read as BAC.

Maine OUI-Defense Attorneys at WTB Law

Each one of these models, however, has drawbacks and unreliable aspects to it that can be challenged to defend against a charge of operating under the influence (OUI) in Maine.

OUI-defense attorney William T. Bly has taken courses on how breath testing machines work, giving him insight on how to best challenge BAC evidence, however it was gathered. Contact him online or call his law office at (207) 571-8146 for the legal defense you need.

About the Author

William Bly

William T. Bly, Esq. is a graduate of Rutgers College where he majored in Political Science with a minor in U.S. History. Attorney Bly attended and graduated the University of Maine School of Law. During his time in law school, Attorney Bly focused on criminal defense.


There are no comments for this post. Be the first and Add your Comment below.

Leave a Comment

Contact Us Today

What distinguishes our Firm from the numerous law firms throughout the state is that we genuinely care about the well-being of our clients. The staff and attorneys of WTB LAW ensure that every client receives hands-on and personalized attention throughout the life of their case.