How Does a Breathalyzer Work?

Most people will never know how a breathalyzer works, at least not from personal experience. This is a good thing, considering that this modern piece of equipment is designed to detect the amount of alcohol in a person’s system. Most of the breathalyzers in use today are in the hands of law enforcement officers, of course.

The word “breathalyzer” is widely recognized as a common term for the device but this is really a brand name introduced by Smith and Wesson decades ago. Even this early model wasn’t the first device used to single out people who have been drinking. Another company manufactured a meter of similar design in the late 1930s.

Common Name

Breathalyzer has become the street name for any device that measures blood-alcohol content, in spite of its being the name of a company’s product. These small pieces of equipment detect alcohol when a person breaths into the mouthpiece or tube because alcohol remains in the body tissue (mouth, lungs, stomach) long after it is ingested. It eventually leaves the body through breathing and from excretion. But if the test is taken soon enough after someone drinks alcohol in the system can measured rather accurately.

Remember, we are talking about blood-alcohol content (BAC). This is the term you will see most often associated with the device. Basically, the breathalyzer “scans” the sample and determines a ratio of alcohol in the breath to alcohol in the blood. Once this comparison is made the person conducting the test can read the amount of alcohol in the blood as a percentage.

It’s crucial that there be no other substances in the mouth when the breath test is taken. Actually having blood, vomit or other liquid in the mouth can skew the results considerably. Keep in mind that alcohol in the blood doesn’t show immediately after the drink is consumed. Police officers have even found that radio signals and cell-phone signals can skew the readings of these electronic devices.

In the Field

Breath tests are often taken on the side of the road, after a police officer stops a driver. Hand-held devices are used for this test. When the driver agrees to the test, he or she exhales into the mouthpiece or tube (breaths into it). A specific type of electro-chemical cell in the device can detect the presence of particular chemicals, such as the alcohol in most beverages. Infrared spectrophotometers are also part of many breath-test devices.

These sensors determine the percentage of alcohol in the breath sample and convert this to a figure that corresponds to the percentage of alcohol in the bloodstream. If that percentage is at or above a specified level the person is determined to be intoxicated. Many people are familiar with the .08 blood-alcohol level as determined by these devices.

Though breathalyzers are most often used by law enforcement, there are models available to the public. Businesses and individuals may use them for measuring the blood-alcohol level of a customer or a family member who has drinking problems.