A breathalyzer is a device used to estimate blood alcohol concentration (BAC) by measuring the amount of alcohol in a person’s breath. Law enforcement uses these devices to determine if a driver is impaired, and they also find use in workplace testing and personal monitoring. This article explores alcohol’s journey through the body, how breathalyzers detect it, and factors influencing detection time.
Alcohol’s Path Through the Body
When alcohol is consumed, it is not digested like food; instead, it is absorbed directly into the bloodstream. About 25% of alcohol enters the bloodstream from the stomach, with most absorbed from the small intestine. Absorption speed varies based on alcohol concentration and carbonation.
Once alcohol enters the bloodstream, it circulates throughout the body, reaching organs like the brain, heart, and muscles within minutes. The liver is the main organ metabolizing over 90% of consumed alcohol. Liver enzymes, such as alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH), break down alcohol into acetate, then eliminated as carbon dioxide and water.
A small percentage of alcohol, typically between 2% and 10%, is not metabolized by the liver but is eliminated from the body unchanged. This occurs through urine, sweat, and breath. Alcohol evaporating in the lungs and expelled during exhalation is what breathalyzers detect.
How Breathalyzers Work
Breathalyzers operate on the principle that the amount of alcohol in a person’s breath is directly proportional to the amount of alcohol in their blood. When alcohol-containing blood circulates through the lungs, alcohol diffuses from the blood into the air in the tiny air sacs called alveoli. This air is then exhaled and measured by the device.
Different breathalyzer technologies exist, but two common types are fuel cell devices and infrared spectroscopy instruments. Fuel cell breathalyzers use an electrochemical reaction to oxidize alcohol in the breath, generating an electrical current proportional to the alcohol concentration. Infrared spectroscopy devices measure alcohol by detecting the absorption of infrared light by alcohol molecules in the breath sample. Both methods provide a breath alcohol concentration (BrAC) reading, used to estimate the blood alcohol concentration (BAC).
Variables Affecting Detection Time
The time it takes for alcohol to show up on a breathalyzer and how long it remains detectable varies considerably among individuals due to several factors. The amount of alcohol consumed and the speed at which it is ingested significantly impact absorption. Rapid consumption leads to a quicker rise in blood alcohol levels and higher peak concentrations.
Food intake plays a role in slowing down alcohol absorption. When alcohol is consumed with food, especially meals rich in fat, protein, and fiber, the food obstructs alcohol from contacting the stomach lining, delaying passage into the small intestine where most absorption occurs. This can reduce the rate at which alcohol enters the bloodstream, sometimes by as much as 75% compared to drinking on an empty stomach.
Body weight and composition also influence alcohol distribution and detection. Alcohol distributes throughout the water in the body, so individuals with more body water content will have a lower concentration of alcohol in their blood for a given amount consumed. Since women generally have a higher percentage of body fat and less body water than men, they may achieve higher blood alcohol concentrations even when consuming the same amount of alcohol adjusted for body weight.
Individual metabolism, primarily driven by liver enzyme activity, dictates the rate at which alcohol is processed and eliminated from the body. While the liver metabolizes alcohol at a fixed rate, approximately 0.015 grams per 100 milliliters per hour (or about half an ounce per hour), this rate can vary due to genetic factors and previous alcohol exposure. Hydration levels can have a minor effect; however, drinking water does not speed up the elimination of alcohol from the bloodstream. Certain medications can also interfere with alcohol processing, either by affecting absorption or metabolism, potentially altering detection times.