Breathalyzer Tests: How Do They Work and Are They Really Accurate?

Breathalyzer tests are essential tools for those in law enforcement who need to test the blood alcohol level of a person suspected of impaired or drunk driving. The breathalyzer testers used to collect samples are small infrared spectrometers. They include small but powerful computer processors to analyze and process sample data and determine when a person could have had more than the legal limit to drink.


How Does a Breathalyzer Test Work?

Breathalyzer Tests PoliceAlcohol is absorbed into the bloodstream and circulated throughout the body. Part of the alcohol is converted into vapor and released through the lungs. It is the vapor that is measured and tested when given a breathalyzer.

The breathalyzer device is calibrated in such a manner to detect the infrared wavelength of alcohol—namely, the ethyl alcohol group—as this is what is used in alcoholic beverages. As you exhale into the device, the air passes through a chamber where the infrared beams look for and measure the wavelength of alcohol.

Depending on the model of breathalyzer device used, it is not uncommon to have a person continue to exhale into the device for several seconds to ensure better accuracy of the test results. Based on the level of alcohol detected, the microprocessor in the minicomputer does some very complex mathematical computations to determine the percentage of Blood Alcohol Concentration (BAC) in the body.

For instance, in California, for someone aged 21 or older with test results that are 0.08% BAC or higher, that person is considered legally impaired. He or she will be arrested and charged with the appropriate Driving Under the Influence (DUI) offense.


How Accurate Are Breathalyzer Test Results?

For the most part, breathalyzer testers provide fairly accurate results in regards to detecting the percentage of blood alcohol concentrations in the body. However, there have been issues with the infrared breathalyzer devices where they do occasionally provide false-positive results.

The devices are not complex enough to detect the actual ethyl alcohol molecules that are used to make alcoholic beverages. Rather, they currently are only able to detect a part of the ethyl alcohol molecule—the part that is related to methyl alcohol types.

Methyl alcohol consists of a much broader spectrum of alcoholic compounds, which could include:

  • Butane
  • Acetone
  • Methane
  • Isopropyl Alcohol
  • Acetaldehyde
  • Propylene

Some of these compounds are found to occur in the body naturally, may be used in various forms of medications, can be the result of certain medical conditions, or for other factors, such as:

  • Diabetes
  • Asthma/Respiratory Conditions
  • Allergies
  • Flu/Cold Medicines
  • Crohn’s Disease
  • Regular Tobacco Use
  • Recent Use of Mouthwash
  • Alcoholism
  • Fasting/Not Eating Regularly
  • Weight Reduction/Weight Loss Diets
  • Prescription Inhalers

When there are other methyl alcohol types present during a breathalyzer test, it can alter the test results. The machine will analyze and process the other methyl alcohol types like they were ethyl alcohol.

In other words, the non-illegal types of methyl alcohol will have a cumulative effect on the test results. It could make it appear people were legally intoxicated even though they might not have consumed any alcohol whatsoever.

Since the testing device cannot distinguish between the different methyl alcohol types, one could find themselves being charged with a DUI, even when legally sober. However, some newer breathalyzer devices can distinguish between other types of methyl alcohol when the test is being processed. The devices will register the test results as unsatisfactory, rather than give a false positive.

In addition, the police are required to maintain records for all breathalyzer testers. These records track how often the device has been used, when it was last recalibrated, and other such details. Here in California, police must do calibration testing every ten days or after one hundred tests, whichever occurs first.

Calibration ensures the device is working accurately and helps reduce the likelihood of potential false positive results. Furthermore, police may request a person submit to more than one breathalyzer test or provide a blood sample.


Why One May Be Asked to Take a Breathalyzer Test

There can be different situations when someone will be asked to provide a breath sample and blow into a breathalyzer device. Of course, the most common one is if they are stopped by the police for erratic and irregular driving, such as weaving back and forth in a lane.

The laws in California require a person to present a sample for testing. If they refuse, they can still be arrested and charged with a DUI offense. It is a common misconception that by refusing to provide a sample for testing, one will not be arrested or charged with driving while under the influence.

Another situation where someone could be required to submit a sample is if they were responsible for an auto accident. If the police notice behavior or other signs that could imply they are impaired, they will be asked to provide a breath sample.

Other situations where one may be asked to give a breath sample to test for alcohol could include:

  • Casusing an accident on the job that resulted in personal injuries.
  • Being on probation for another type of criminal offense, and part of their release stipulates they cannot drink.
  • Their employer placed them on probation as a result of a drinking problem and requires testing to ensure compliance.
  • Prior conviction of a DUI offense and requires use of an interlock device in their vehicle.


If you or someone you know requires an SR22 insurance certificate to get their license reinstated for a DUI or other state-mandated requirements, please feel free to contact Breathe Easy Insurance at 866.822.7755 today!