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How does a breathalyzer function?Adey Hill:
A breathalyzer, or intoxilyzer, is essentially an altered infrared spectrometer.
Before we dive into the details, let's first discuss alcohol and its journey into your bloodstream and breath: Alcohol refers to a category of organic compounds. Ethanol, the type of alcohol found in alcoholic drinks, is a relatively small molecule, which makes it easy for it to be absorbed from the stomach into the bloodstream. As alcohol is volatile and the body maintains warmth, each time you exhale, some of the alcohol in your blood turns into vapor and enters the alveoli of your lungs, eventually leaving your body. The more alcohol you consume, the more alcohol vapor is released.
Organic compounds absorb infrared radiation (IR) at various wavelengths, each with a unique IR signature. The infrared (IR) spectrometer in intoxilyzers is calibrated to the specific wavelength at which ethanol absorbs it.
When you breathe into an intoxilyzer, the air you exhale enters a sample chamber. If you've been drinking, some of the alcohol from your blood will also be present in your breath. In the case of the Lion Intoxilyzer 6000s by Lion Labs, the device starts sampling as soon as the breath enters the chamber, measuring it 37 times per second. The machine continues this process until you blow a continuous reading for three seconds. This ensures the sample is taken from deep lung air, where the highest alcohol concentration is found. Once this is achieved, the machine confirms a sufficient sample and proceeds to the next phase (either a second sample or a calibration check).
The air inside the sample chamber is analyzed by a beam of infrared radiation (with an IR detector positioned behind the chamber). The machine measures the amount of IR directed at the chamber and calculates how much was absorbed. Some advanced calculations determine how many micrograms of alcohol are in 100 ml of breath. This result is then displayed.
A few additional details about breathalyzers: These devices can detect other substances like methanol, isopropyl alcohol, or acetone. If these substances are present in significant amounts, the machine will recognize them as interfering and the sample will be considered invalid.
The breath tube, which you blow into using a disposable mouthpiece, is preheated to a precise temperature to ensure the samples adhere to Boyle's law, making the readings consistent and accurate each time.
The machines are capable of detecting mouth alcohol. If you've recently consumed alcohol or used an alcohol-based mouthwash, the device will pick it up. The intoxilyzer begins sampling as soon as you exhale, so it will register a high alcohol concentration at the start of the test, followed by a drop (on a graph). This spike alerts the machine that the initial sample contained more alcohol than the rest, indicating the presence of mouth alcohol.
You can't fool or bypass the intoxilyzers by trying to blow around the sides of the mouthpiece, covering it with your tongue, or placing something like a copper coin in your mouth beforehand. The only sure way to avoid detection is simply not to drink and drive!
This post originally appeared on Quora. Click here to view.
