Have you ever been pulled over by the police after a night out and asked to blow into a little device? Chances are, it was a breathalyzer – that nifty gadget cops use to figure out if you’ve had a few too many drinks before getting behind the wheel. But how exactly do these alcohol breath tests work their magic? Let’s dive in and demystify the science behind this common roadside ritual.
The Basics: Alcohol in Your Breath
First things first – despite what you might think, breathalyzers don’t actually measure the alcohol content in your blood directly. Instead, they rely on a sneaky principle called Henry‘s Law. In simple terms, this law states that the concentration of a volatile substance (like alcohol) in the air above a solution (like the liquid in your lungs) is proportional to the concentration of that substance in the solution itself1.In other words, the amount of alcohol vapor in your breath can tell us a whole lot about how much of the hard stuff is actually coursing through your veins. When you knock back a cold one, the alcohol gets absorbed into your bloodstream through the lining of your stomach and small intestine. From there, it hitches a ride in your blood to various organs, including your lungs.As your booze-infused blood passes through the tiny air sacs in your lungs, some of the alcohol molecules jump ship and evaporate into the air you breathe out. The higher your blood alcohol concentration (BAC), the more alcohol will be exhaled in your breath. Breathalyzers are designed to capture and measure this exhaled alcohol, giving police a quick and easy way to estimate your BAC without having to stick you with a needle.
The Magic Number: Blood Alcohol Concentration
Okay, so breathalyzers measure the alcohol in your breath – but what do those numbers actually mean? In most states, the legal BAC limit for driving is 0.08%2. That tiny percentage refers to the number of grams of alcohol per 100 milliliters of blood. So if you blow a 0.08 on a breathalyzer, it means there are roughly 0.08 grams of alcohol in every 100 milliliters of your blood.To put that in perspective, a standard drink (like a 12-ounce beer, 5-ounce glass of wine, or 1.5-ounce shot of liquor) contains about 14 grams of pure alcohol2. So if you weigh 160 pounds, just two drinks in an hour could be enough to push you over the legal limit. Of course, factors like your sex, weight, metabolism, and how much you’ve eaten can all affect how quickly your BAC rises and falls.
Under the Hood: How Breathalyzers Do Their Thing
Now that we’ve covered the basics, let‘s geek out over the actual technology behind breathalyzers. There are a few different types on the market, but most use one of two methods to measure alcohol: fuel cell sensors or infrared spectroscopy.
Fuel Cell Breathalyzers
Fuel cell breathalyzers, like the popular Intoxilyzer brand, work by causing a chemical reaction between the alcohol in your breath and a special electrode coated with a porous layer of platinum oxide1. When you blow into the mouthpiece, your breath is funneled into a chamber containing two electrodes – one coated with the platinum oxide, and one made of pure platinum.As the alcohol in your breath reacts with the platinum oxide, it produces acetic acid, protons, and electrons1. The electrons flow through a wire from the platinum oxide electrode to the pure platinum electrode, generating an electrical current. The higher the concentration of alcohol in your breath, the stronger the current will be. The breathalyzer measures this current and uses it to calculate your approximate BAC.One advantage of fuel cell breathalyzers is that they’re specific to ethanol (the type of alcohol found in booze). They‘re less likely to be fooled by other substances in your breath, like acetone from diabetes or certain low-carb diets5. However, they do require regular calibration to stay accurate over time.
Infrared Breathalyzers
The other common type of breathalyzer uses infrared spectroscopy to measure alcohol concentrations. Instead of a chemical reaction, these devices rely on the fact that different molecules absorb light at different wavelengths1.When you exhale into an infrared breathalyzer, your breath passes into a chamber with an infrared lamp on one end and a detector on the other. The lamp shines a beam of infrared light through the breath sample, and the detector measures how much of that light makes it through to the other side.Ethanol molecules happen to absorb infrared light at a specific wavelength (around 3.4 micrometers)3. The more alcohol there is in your breath, the more infrared light will be absorbed, and the less will reach the detector. By measuring the amount of infrared light that‘s absorbed, the breathalyzer can estimate the concentration of alcohol in your breath and, by extension, your blood.One potential issue with infrared breathalyzers is that other substances in your breath (like acetone) can also absorb infrared light and skew the results4. To get around this, most devices use complex algorithms to distinguish between alcohol and other compounds. Some also have built-in safeguards, like aborting the test if they detect mouth alcohol from a recent sip of booze3.
Ensuring an Accurate Sample
Speaking of mouth alcohol, let’s talk about some of the ways breathalyzers try to ensure they‘re measuring the alcohol in your deep lung air, not just the residual booze in your mouth.When you first start to exhale, the air coming out of your mouth is mostly from your upper airway and trachea. This air hasn’t had a chance to equilibrate with your blood alcohol levels yet, so it’s not a great sample for estimating your BAC. That’s why officers will usually have you blow for a good 4-5 seconds before taking a reading – they want to make sure they‘re capturing your alveolar air from deep in your lungs3.Some breathalyzers also have a built-in slope detector that monitors your breath alcohol concentration throughout the entire exhalation. If there’s a sudden spike in alcohol right at the beginning (indicating mouth alcohol), the device will usually abort the test and make you try again3. This helps prevent artificially high readings from that shot you took right before the cop pulled you over.
Can You Beat the Breathalyzer?
We’ve all heard rumors about ways to trick a breathalyzer – sucking on a penny, chewing gum, or even hyperventilating before the test. But do any of these urban legends actually hold up?The short answer is no – at least not reliably. Some studies have shown that hyperventilating or taking a big gulp of air right before the test can temporarily lower your breath alcohol concentration, but the effect is usually short-lived and not enough to get you out of a DUI4. Plus, most officers are trained to watch for these kinds of shenanigans and will just make you wait a few minutes and test you again.Other common myths, like using mouthwash or breath mints to mask the smell of alcohol, are even less likely to work. If anything, the alcohol in mouthwash could actually boost your breath alcohol reading and make you look even more intoxicated4. And while popping a mint might make your breath smell better, it won‘t do anything to change your BAC.At the end of the day, the only surefire way to “beat” a breathalyzer is to not drink and drive in the first place. If you do choose to imbibe, always have a designated driver, call a cab or ride-share, or stay put until you‘ve sobered up. No amount of gum-chewing or penny-sucking is worth the risk of getting behind the wheel impaired.
