How do breathalyzers work

We often hear or read about accidents that occur because of a driver’s DUI, and in news reports of the accident, it is often stated what the driver’s blood alcohol content was and what the legal limit for blood alcohol is. For example, a driver may be tested with a blood alcohol level of .15, while the legal limit is .08. But what do these numbers mean? How do police officers determine whether a driver suspected of DUI is legally ingesting? You may have heard of a breathalyzer, however you are more interested in knowing how a person’s exhaled gas indicates their alcohol intake.

With public safety in mind, it is important to prohibit drivers from drinking and driving. In 1999, 42,000 people died in traffic accidents in the U.S., and 38 percent of those deaths were alcohol-related. Even drivers who are able to pass the sobriety tests by touching their noses or walking in a straight line may still exceed the legal limit of blood alcohol content and become roadkillers. As a result, police officers use some of the latest technology to detect the BAC of drivers suspected of DUI and take them off the road.

Many on-duty traffic police officers utilize breath alcohol testing devices (a breathalyzer is one of them) to determine the blood alcohol concentration (BAC) of suspected drunk drivers. In this article, we will examine these How do breathalyzers work.

How do breathalyzers work
How do breathalyzers work

Why you should be tested

The legal basis for driving under the influence is the blood alcohol concentration (BAC) level. However, taking a blood sample at the scene and then analyzing it in a lab is neither practical nor efficient for detaining a driver suspected of driving while intoxicated (DWI) or driving under the influence (DUI). Urine alcohol testing has proven to be as impractical as blood sampling. What was needed was a method that could measure the indicators associated with blood alcohol concentration without invading the driver’s body.

Breathalyzers were first invented for police use in the 1940s. in 1954, Dr. Robert Borkenstein of the Indiana State Police invented breathalyzers, which are still used by law enforcement agencies today.

Let’s take a look at what these devices are based on to work.

FS00701-5
Electrochemical C2H5OH Alcohol Sensor Module FS00701

The Test Principle

Alcohol that a person drinks is absorbed into the bloodstream by the mouth, throat, stomach, and intestines, and then exhaled out of the body in the form of breath.

Alcohol is not digested or chemically changed in the bloodstream after ingestion. Because alcohol is volatile, it is able to evaporate from the blood as it flows through the lungs, so some alcohol passes through the alveolar membrane into the gas inside the alveoli. The concentration of alcohol in the alveolar gas correlates with the concentration of alcohol in the blood, and when the alcohol in the alveolar gas is exhaled, it can be detected by a breathalyzer device. Traffic police do not have to take the driver’s blood to test the alcohol content in their body, but by testing the driver’s breath on the spot, they can immediately know whether the driver is a drunk driver.

Because the concentration of alcohol in the breath is related to the concentration of alcohol in the blood, the traffic police can calculate the BAC by measuring the amount of alcohol in the breath. The ratio of alcohol in the breath to alcohol in the blood is 2,100:1.This means that 2,100 milliliters of alveolar air contains the same amount of alcohol as 1 milliliter of blood.

The American Medical Association says that the body is impaired when the blood alcohol concentration reaches 0.05. If a person’s blood alcohol concentration measures 0.08, that means 0.08 grams (80 milligrams) of alcohol per 100 milliliters of blood.

FS00702-6
Electrochemical C2H5OH Alcohol Sensor Module FS00702

How do breathalyzers work

Usually, the driver being tested breathes into the breathalyzer for more than 2.5 seconds, and the law enforcer only needs to observe the change in the value of the instrument to make a preliminary inference of whether the person being tested is a drunk driver or a drunk driver. This is because the alcohol detector is equipped with an Alcohol Sensor, which is equivalent to a gas-sensitive resistor, the resistance value will change with the change of alcohol concentration in the exhaled gas of a person, thus causing changes in the current and voltage in the circuit. The alcohol content in the exhaled gas and blood alcohol content has a certain proportional relationship, different concentrations of the alcohol content will cause the sensor to produce different strengths of the voltage signal, and finally, the signal is amplified through the electronic amplifier, but also to get the data on the alcohol detector.

The breath alcohol detector is developed from the original drunkenness tester, tester, and portable drunkenness detector. The first breathalyzer was developed back in 1954. Since then, breathalyzers have begun to evolve rapidly, while alcohol sensor technology has continued to improve.

At present, the commonly used breath alcohol detector products, the sensor technology used in the main five, respectively, semiconductor detection technology, fuel cell type technology, colorimetric technology, infrared detection technology, and gas chromatography technology. Due to various reasons, the most commonly used are fuel cell technology and semiconductor detection technology.

Fuel cell-type breath alcohol detector uses fuel cell alcohol sensors as the gas-sensitive element. In fuel cell alcohol sensor using platinum as the electrode, the sensor combustion chamber is filled with a special catalyst, which can make the combustion chamber into the full combustion of alcohol into electrical energy, but also in the two electrodes to produce voltage, this voltage and into the combustion chamber gas alcohol concentration is proportional.

Semiconductor sensor breath alcohol detector is generally used tin oxide semiconductor sensor. When the concentration of the sensitive gas in the measured gas increases, the gas-sensitive nature of the tin oxide semiconductor sensor results in a decrease in the resistance value.

Fuel cell-type Breathalyzers are more expensive to produce but have better performance than semiconductor sensor Breathalyzers. Breathalyzers with different technologies are constantly being updated to keep everyone safe on the road.