alcometer

An alcometer, often spelled alcoholometer, is a device used to estimate a person's blood alcohol concentration (BAC) by measuring the amount of alcohol in a breath sample. It is commonly used by law enforcement to enforce drunk-driving laws, and in workplaces and medical settings to assess impairment.

Principle: Most contemporary alcometers are breath analyzers. They either use electrochemical sensors (fuel-cell or amperometric sensors) or infrared spectroscopy to detect ethanol in exhaled air. The device reports a breath-alcohol concentration, which is converted to an estimated BAC using a standard breath-to-blood partition ratio (traditionally about 2100:1 in many systems; actual ratios vary by system and individual physiology).

Types and use: Evidential breath testers (EBTs) are calibrated and often used by police; portable handheld units are common for roadside checks or workplace testing. Some devices are designed for personal use and may provide estimated BAC or percent alcohol by volume in the breath. Results are typically expressed as mass per volume of blood (e.g., g/dL or mg/L). Mouth alcohol, recent drinking, temperature, and device calibration can affect readings.

Calibration and limitations: Regular calibration with standard gas or solutions is required for accuracy. Devices must be maintained, and proper mouthpiece hygiene is important to avoid contamination. Breath testing is a screening tool; confirmatory blood tests may be used in legal settings.

History: The modern breathalyzer was developed in the 1950s by Robert F. Borkenstein, expanding the ability to assess intoxication without drawing blood.

See also: Breathalyzer, blood alcohol content, intoxication law.