By Andrea Cohen, Tests.com Contributing Writer
In order to determine a person’s level of alcohol intoxication, their blood alcohol content or concentration is measured. The only way to get an exact measurement of blood alcohol levels is through a blood sample, but since this is not always a practical method for determining how intoxicated a person is, a breath analyzer test is used to estimate blood alcohol content.
Breathalyzer is actually the brand name of a particular product. There are many other manufacturers that offer instruments that analyze breath samples to estimate blood alcohol content, but the term “breathalyzer” has been generally used to refer to all models of breath alcohol analyzers.
How the Breathalyzer Test Works
A breathalyzer test estimates the blood alcohol content in a person’s body based on a breath sample. Alcohol that is absorbed into the body shows up in the breath of a person and can give an indication of the amount of alcohol that is concentrated in the bloodstream. Alcohol is not immediately digested or chemically changed upon absorption, and as the blood goes through the lungs, some of the alcohol in the lungs is exhaled into the air. The ratio of breath alcohol to blood alcohol is 2,100:1.
All breathalyzer devices have a mouthpiece, usually a plastic tube or straw, which is used to blow air into a chamber in which the air is analyzed. A gauge provides a readout of the estimated blood alcohol content, although some readouts are digital and others are based on a color chart.
The legal limit for drunkenness in the United States is 0.08 grams of alcohol per 100 ml of blood. However, the American Medical Association claims that a person can become impaired when their blood alcohol level reaches just 0.05.
Types of Breath Alcohol Analyzer Devices
There are a few primary types of breath analyzer devices for determining blood alcohol levels in the body, each based on a different technology:
- Breath testers produce color changes through a chemical reaction involving alcohol. They contain two glass vials that have a mixture that makes a chemical reaction when alcohol is present in the reaction chamber. Photo cells in the device measure the color change associated with the chemical reaction to determine the level of alcohol that is measured in the breath sample and display it on a scale.
- Infrared testers detect alcohol in a breath sample by using infrared spectroscopy. This technology works by identifying how molecules absorb infrared light. Each type of bond within a molecule absorbs infrared light at different wavelengths, so in order to determine if there is ethanol (alcohol) in a breath sample, the amount of infrared absorption is measured. This provides information about the molecule structure and identifies whether the substance contains ethanol (C-O, O-H, C-H, C-C).
- Fuel cell technology uses fuel cells to detect chemical reactions of alcohol. These fuel cells have two platinum electrodes on either side of a porous, acid-electrolyte material. As the air flows past one side of the fuel cell, the platinum oxidizes any alcohol that’s in the air and produces acetic acid, protons and electrons. The electrical current that is established between the two electrodes can reveal the presence of alcohol in the air sample.
- Semiconductor devices also use a current to determine the presence of alcohol. A small, charged bead of tin oxide is headed to 300 degrees Celsius. When alcohol comes into contact with the bead, the current changes. The degree of change determines the concentration of alcohol in the breath.
Accuracy of Breathalyzer Tests
Research has indicated that breath analyzer test results can vary by at least 15% from actual blood alcohol concentration. There are a number of factors that can affect the results of breath alcohol analyzer tests and can produce inaccurate readings. Some of these factors include:
- Human or device error – Machines may be used incorrectly or the devices may not be maintained or re-calibrated as required.
- Breathing pattern – Tests have shown that holding your breath prior to taking the test can increase results, while hyperventilation prior to a test can decrease readings of BAC.
- Temperature – False readings may be obtained if the device is not properly calibrated for surrounding air temperature or body temperature.
- Some products skew results – Usage of mouthwash, breath spray or other products containing alcohol will falsely raise test results. The alcohol in these products usually dissipates after two minutes, but studies have shown that their effect can last longer. Some law enforcement officials have regulations regarding how soon they can perform breathalyzer tests after an individual eats, vomits or puts something in their mouth. This time limit is usually about 15 minutes.
- Differences among people – Breathalyzers assume a certain ratio between breath alcohol content and blood alcohol content in people to determine a blood alcohol content reading. This will not necessarily apply to all people for a variety of reasons and can produce inaccurate results.
Breathalyzers for Consumers
Quite a few models of breathalyzers have been manufactured for use by consumers. They are hand-held devices which are smaller and less expensive than those used by law enforcement officials. Rather than using electrochemical fuel cell analysis, these devices usually use silicon oxide sensors. Breathalyzers sold to consumers must be certified by the Food and Drug Administration if sold in the United States. Models range in price from under $100 up to a few hundred dollars.
Breathalyzers for Law Enforcement
Law enforcement officials may use desktop or hand-held breathalyzers to determine blood alcohol content. The smaller, hand-held breathalyzer devices are an easy way to quickly determine whether someone is impaired by alcohol in tests referred to as field sobriety tests. Most breath analyzers used by law enforcement use either electrochemical fuel cell technology or infrared spectrophotometer technology. Models used for law enforcement purposes must be approved by the National Highway Traffic Safety Administration, which falls under the United States Department of Transportation.
Are you considering purchasing a personal breathalyzer test device? Take a look at our Breathalyzer Test Directory to find the right one for you. For more on the breathalyzer, please see our interviews with breathalyzer experts Nima Parto, Ed Gollar and Barry Knott.
Sources: American Medical Association, ama-assn.org; National Highway Traffic Safety Administration, nhtsa.gov; United States Food and Drug Administration, fda.gov; Lifeloc Technologies, lifeloc.com