Like HowStuffWorks on Facebook!

How the iBreath Alcohol Breathalyzer Works

The iBreath Alcohol Breathalyzer plugs into the base of an iPhone. See more pictures of essential gadgets.

After a night out on the town filled with fun and a little alcohol consumption, how is a hipster supposed to know if it's safe to get behind the wheel of a car? If the hipster happens to own an iBreath Breathalyzer, the answer could be just a puff of air away.

The iBreath Alcohol Breathalyzer is a handy little device that you can plug into the base of an iPhone or iPod. It features a small light-emitting diode (LED) screen, six simple buttons and a flip-out tube. After activating the breathalyzer function, you can blow a steady stream of air into the tube and the device will give you a readout of your estimated blood alcohol content (BAC). To top it all off, the device also has an FM transmitter.

The device doesn't send data to your iPhone or iPod. The connection between the two devices serves two purposes. First, it provides power to the iBreath analyzer. Second, you can use the transmitter function to broadcast tunes from your iPhone or iPod to a nearby radio. But if you don't have your phone or MP3 player handy, you can also use a USB cable or 12-volt car plug to power the device.

The iBreath Breathalyzer estimates your BAC by detecting and measuring the presence of ethanol vapor in your breath. There's a relationship between the amount of alcohol in a person's breath and the amount you'd find in that person's blood. Since alcohol impairs your ability to operate vehicles safely and make sound judgments, national law in the United States says that driving with more than .08 grams of alcohol per 100 milliliters of blood is prohibited. The accepted estimated ratio between breath alcohol and blood alcohol levels is 2,100:1 [source: Stowell, et al.].

Traditionally, devices that estimate BAC from the alcohol content in a person's breath rely on one of three methods. The breathalyzer method determines alcohol levels by monitoring a chemical reaction that occurs in the presence of alcohol. Intoxilyzers use infrared spectroscopy to detect and measure alcohol levels, and alcosensors monitor chemical reactions within a fuel cell to take alcohol content measurements. But the iBreath relies on a different detection method.