How Do Breathalyzers Work?

Alcohol breath tests, or breathalyzers, measure how much alcohol is in a person’s breath, which can help measure the amount of alcohol in someone’s blood. Breathalyzers contain a reddish-orange solution made of potassium dichromate. When the potassium dichromate solution reacts with alcohol, it turns green. The degree of color change depends on the amount of alcohol on someone’s breath. A photocell inside the breathalyzer machine compares the colors of the reacted mixture to an unreacted mixture, the difference in color produces an electrical current, and the electrical current is converted into a number – BAC or blood alcohol content.

In all 50 states, the District of Columbia, and Puerto Rico, driving with a BAC of 0.08 or higher is illegal. As such, police officers use breathalyzers to indirectly measure how much alcohol is in a person’s blood.

How Does the Amount of Alcohol in Exhaled Breath Indicate the Amount of Alcohol in the Blood?

When someone drinks alcohol, it enters the blood quickly via the stomach and small intestine. That blood passes in front of tiny air sacs in the lungs (alveoli), and the alcohol is exhaled through the breath. Approximately 90% of the alcohol we drink is broken down by the liver and enters our bloodstream. The rest is expelled through urine and breath.

Because this entire process happens so quickly, a person’s BAC can be measured within minutes of having an alcoholic drink. BAC is usually the highest about an hour after drinking.

How Accurate Is a Breathalyzer?

The alcohol breath tests available today are fairly accurate, but they are not perfect. Additionally, failure to use breathalyzers correctly can lead to serious mistakes. Drivers who are barely above the legal limit may have a defense for unfavorable breath tests, as all breathalyzers have a margin of error.

Tainted breath samples can also cause inaccurate BAC readings. For example, you might blow a higher BAC if you just had a drink, and some of the alcohol remains in your mouth. Other substances, like mouthwash, can also register as alcohol.

For this reason, officers must observe the driver for 15 to 20 minutes before administering an alcohol breath test. Failure to honor the observation time could lead to tainted breath samples and flawed results.

When used correctly, top-rated devices are difficult to argue with, but everything from poor maintenance to contaminants in the machine and chemicals in the air can interfere with a breathalyzer’s accuracy.

This is why criminal defense attorneys always look twice at the results of alcohol breath tests.

Charged with a DWI?

If you have been charged with a DWI, our team at Foley Griffin can help you challenge breath test results. Any misuse of a breathalyzer device is enough to have your charges dismissed or win a not-guilty verdict.

We understand how scary facing criminal charges may be, but we are here to help ensure the law works for everyone, and you are innocent until proven guilty.

Discuss your situation with our experienced attorneys during a free consultation – call us at (888) 966-8480 or contact us online to schedule yours today.