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How Breathalyzers Work

There are three major types of breath alcohol testing devices, and they're based on different principles:

Breathalyzer - Uses a chemical reaction involving alcohol that produces a color change

Intoxilyzer - Detects alcohol by infrared (IR) spectroscopy

Alcosensor III or IV - Detects a chemical reaction of alcohol in a fuel cell
Regardless of the type, each device has a mouthpiece, a tube through which the suspect blows air, and a sample chamber where the air goes. The rest of the device varies with the type.

Breathalyzer

The Breathalyzer device contains:

A system to sample the breath of the suspect
Two glass vials containing the chemical reaction mixture
A system of photocells connected to a meter to measure the color change associated with the chemical reaction To measure alcohol, a suspect breathes into the device. The breath sample is bubbled in one vial through a mixture of sulfuric acid, potassium dichromate, silver nitrate and water. The principle of the measurement is based on the following chemical reaction:

In this reaction:

The sulfuric acid removes the alcohol from the air into a liquid solution. The alcohol reacts with potassium dichromate to produce:

chromium sulfate

potassium sulfate

acetic acid

water

The silver nitrate is a catalyst, a substance that makes a reaction go faster without participating in it. The sulfuric acid, in addition to removing the alcohol from the air, also might provide the acidic condition needed for this reaction. During this reaction, the reddish-orange dichromate ion changes color to the green chromium ion when it reacts with the alcohol; the degree of the color change is directly related to the level of alcohol in the expelled air. To determine the amount of alcohol in that air, the reacted mixture is compared to a vial of unreacted mixture in the photocell system, which produces an electric current that causes the needle in the meter to move from its resting place. The operator then rotates a knob to bring the needle back to the resting place and reads the level of alcohol from the knob -- the more the operator must turn the knob to return it to rest, the greater the level of alcohol.

The Chemistry of Alcohol The alcohol found in alcoholic beverages is ethyl alcohol (ethanol). The molecular structure of ethanol looks like this:

h1C - C - O - H

where C is carbon, H is hydrogen, O is oxygen and each hyphen is a chemical bond between the atoms. For clarity, the bonds of the three hydrogen atoms to the left carbon atom are not shown. The OH (O - H) group on the molecule is what makes it an alcohol. There are four types of bonds in this molecule:

carbon-carbon (C - C) carbon-hydrogen (C - H) carbon-oxygen (C - O) oxygen-hydrogen (O - H)

The chemical bonds between the atoms are shared pairs of electrons. Chemical bonds are much like springs: They can bend and stretch. These properties are important in detecting ethanol in a sample by infrared (IR) spectroscopy.

When you retain Jack I. Hyatt, you will get the very best defense from a former assistant states attorney who has prosecuted over 20,000 cases for the State of Maryland, understands both sides of the law and thoroughly knows the state's playbook and procedures.

"I selected Jack Hyatt because of his experience, knowledge and reputation. He thoroughly investigated my case, detected technical mistakes made during my arrest and had my DWI and all other charges completely dismissed at trial. If you are charged with DWI or any traffic charge, he is the lawyer you need to call." Robert E. Schade

"Thank you for your persistence on hard work. After a breath test of 1.5 resulting in 5 charges including DUI, DWI, failure to drive right of center and leaving the scene of an accident, I was totally surprised when you had all 5 charges dismissed at trial. The result was more than I expected or hoped for. I now understand why the first lawyer I called referred me to you." Dr. Ochi.

How Does A Breathalyser Work for DWI in Maryland?

How can a person's breath show how much that person has had to drink?

Alcohol that a person drinks shows up in the breath because it gets absorbed from the mouth, throat, stomach and intestines into the bloodstream. Alcohol is not digested upon absorption or chemically changed in the bloodstream. As the blood goes through the lungs, a physiologically predictable amount of the alcohol will moves across the lung membranes and into the lungs themselves.

Once in contact with the air in the lungs, it evaporates and is exhaled. The concentration of the alcohol in the air in the lungs is directly related to the concentration of the alcohol in the blood.

The ratio of breath alcohol to blood alcohol is 2,100 to 1 (and called the partition ratio), so the alcohol content of 2,100 milliliters of exhaled air will be the same as for 1 milliliter of blood. The maths are simple from there and leads to blood alcohol readings expressed as a percentage of alcohol in the blood.

The partition ratio can vary between 1700 and 2400 depending upon the individual and local environmental conditions, leading to a breath analysis reporting either a higher or lower calculated blood alchol reading.

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