Breath testing for alcohol has become a ubiquitous tool in law enforcement, particularly in cases involving driving under the influence (DUI). This method, often facilitated by a device known as a breathalyzer, plays a crucial role in assessing an individual’s blood alcohol concentration (BAC) quickly and non-invasively.

I. The Science of Breath Testing:

Breath testing is grounded in the principle that alcohol in the bloodstream can be detected through the breath. When a person consumes alcoholic beverages, the ethanol present in the drinks is absorbed into the bloodstream. As blood circulates through the lungs, a fraction of the alcohol is released into the air sacs, and subsequently, expelled through breath.

II. The Breathalyzer and How It Works:

A breathalyzer is a device designed to measure the concentration of alcohol in a person’s breath. There are various types of breathalyzers, but most operate on the same fundamental principles. The device contains a sensor, typically an electrochemical fuel cell or an infrared spectroscopy system, which reacts with the alcohol molecules in the exhaled breath.

In electrochemical fuel cell-based breathalyzers, alcohol undergoes a chemical reaction that generates an electrical current. The magnitude of this current is directly proportional to the concentration of alcohol in the breath, allowing for an accurate BAC measurement. Infrared spectroscopy, on the other hand, relies on the absorption of infrared light by alcohol molecules, providing another method to quantify BAC.

III. Sources of False Positives:

While breathalyzers are generally reliable, certain factors can lead to false positives. Understanding these factors is essential for a more nuanced interpretation of breath test results. Some common sources of false positives include:

a. Mouthwash and Breath Fresheners: Some mouthwashes and breath fresheners contain alcohol, which can influence breathalyzer results.

b. Medical Conditions: Certain medical conditions, such as diabetes or gastroesophageal reflux disease (GERD), may lead to elevated breath alcohol readings.

c. Ketogenic Diets: Individuals on ketogenic diets may experience increased acetone levels in their breath, potentially influencing breathalyzer results.

IV. Breath Testing in Texas:

In Texas, breath testing is a standard practice in DUI investigations. Law enforcement officers are trained to administer breathalyzer tests during traffic stops if they suspect a driver is under the influence of alcohol. The results of these tests can play a crucial role in legal proceedings related to DUI charges.

V. Accuracy of Breathalyzers:

Breathalyzers are generally considered accurate when used correctly. However, it’s important to note that their precision can be influenced by various factors, including calibration, maintenance, and proper usage. Regular calibration and maintenance ensure that the device provides reliable and consistent results. Moreover, officers must follow specific protocols when administering breath tests to minimize the risk of errors.

VI. Legal Implications and Challenges:

Breathalyzer results are often used as evidence in legal proceedings, but challenges to their accuracy have been raised in some cases. Defense attorneys may question the reliability of breath test results by examining factors such as the calibration history of the device, the officer’s training, and adherence to proper testing procedures.


Breath testing for alcohol, facilitated by devices like breathalyzers, has become a cornerstone in law enforcement efforts to combat drunk driving. Understanding the science behind breath testing, the mechanics of breathalyzers, potential sources of false positives, and the application of these devices in Texas is crucial for both law enforcement professionals and the general public. As technology evolves, ongoing research and advancements will likely contribute to further enhancing the accuracy and reliability of breath testing methods.