Breathalyzers

Breathalyzers are devices that estimate a person’s blood alcohol concentration (BAC) from a breath sample. They analyze ethanol in the end-tidal or alveolar portion of the breath and convert that value into an estimate of BAC. They are used by law enforcement, employers, and healthcare professionals to assess intoxication.

Modern breathalyzers employ several sensing technologies. Fuel cell sensors produce an electrical current proportional to ethanol concentration. Semiconductor oxide sensors change resistance in response to ethanol vapors. Some higher-end devices use infrared spectroscopy or laser-based methods for greater specificity. Portable handheld units are common for field work, while more precise instruments termed evidential breath testers are used in police facilities; both require routine calibration and quality checks.

Measurement involves collecting a deep breath and exhaling through a mouthpiece into the device. The alcohol concentration in alveolar air is translated to a BAC estimate, typically using a standard partition ratio (commonly 2100:1). Results are reported as BAC (percent or g per 100 milliliters) or as BrAC with conversion to BAC in some jurisdictions.

Accuracy and limitations: Breathalyzers provide estimates and can be affected by factors such as mouth alcohol from recent drinking, recent food or milk, smoking, ambient temperature, sensor drift, and improper mouthpiece use. Proper calibration, maintenance, and validated operating procedures are essential for reliable results.

Regulation and use: In many countries, breath test results are admissible as evidence when tests are administered by trained personnel and devices are properly calibrated. They are also used in workplace safety programs and clinical settings.

Maintenance: Regular calibration with known ethanol standards, periodic performance checks, cleaning, sensor replacement, and battery maintenance are standard practices.