How the iBreath Alcohol Breathalyzer Works

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


Mechanics of the iBreath Alcohol Breathalyzer

The iBreath device has a special semiconductor sensor chip inside of it that detects and measures alcohol content. Japanese engineers designed the sensor to react in the presence of ethanol gas.

The semiconductor substrate -- in other words, the foundation of the semiconductor -- has a very thin membrane of tin dioxide (SnO2). Connected to this membrane is a small metal heater. The heater is one of the elements in the iBreath device that requires power. The purpose of the heater is to warm the membrane to the optimal operating temperature. It turns out that ethanol sensors require heat to detect the presence of alcohol with accuracy. They also require isolation -- if the sensor loses heat during operation, it can give a false reading.


When ethanol gas comes into contact with the tin dioxide membrane, the membrane absorbs the ethanol molecules. The tin dioxide reacts with the alcohol molecules and its electrical resistance changes. The semiconductor measures the difference in resistance and generates an estimate of the user's BAC. Through multiple trials in the lab, engineers determined the relationship between the difference in the electrical resistance of tin dioxide and the density of ethanol within a gas. The iBreath's LED screen displays the estimate.

In addition to the breathalyzer function, the iBreath comes with an FM transmitter. When you plug the iBreath into an iPhone or iPod, it draws power from the device and can also accept data from the songs you've stored on it. The transmitter converts the data signal into a low-power radio frequency. If you tune a nearby radio to the same frequency, you'll be able to hear the music from your phone or MP3 player without tethering the device with a cable.


Using the iBreath Alcohol Breathalyzer

To use the iBreath, you first have to make sure it's drawing power. The iBreath doesn't have its own batteries, but there are several ways to power the device:

  • Plug it into an iPod or iPhone.
  • Use a USB cord and connect the device to a computer.
  • Use the provided 12-volt car plug and connect the iBreath to your vehicle.

Once the iBreath has power, it's ready for operation. To use the breathalyzer function, you need to unfold the blow wand from the device. Next, you press the ENT button on the iBreath and a 10-second countdown begins. During this countdown, the tiny heating element inside the iBreath warms the gas sensor tin dioxide membrane to the appropriate temperature.


Once the sensor is ready, it's time to breathe into the wand. You need to blow a steady stream of air into the wand for about 10 seconds. The semiconductor chip will react to any alcohol in your breath and measure the resulting change in resistance. The LED screen will display your estimated BAC. If it's near or above .08, you shouldn't even think about getting behind the wheel of a car.

The iBreath also has a simple timer function that will help remind you to test your BAC again. If you've had one beer too many, you may need to take another test in about an hour. Setting the timer on the iBreath will help keep you on track. When the timer goes off, you can repeat the test.

If you want to use the FM transmitter, simply push the Mode button on the device. The iBreath has two tuning buttons that let you adjust the frequency of the transmitter so you get the best result. Using a combination of these buttons and the ENT button will let you set the radio frequency. Once you find an available channel, pressing the lock button will keep the device tuned to that frequency even if you accidentally hit one of the other buttons.

Using devices like the iBreath can help prevent you from making a serious mistake in judgment. Remember that driving under the influence is both dangerous and illegal.

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Lots More Information

Related HowStuffWorks Articles

  • "Alcohol Gas Sensor."
  • "iBreath Breathalyzer & FM Transmitter for iPod & iPhone." (April 21, 2009)
  • Stowell, A.R.,  A.R. Gainsford and R.G. Gullberg. "New Zealand’s Breath and Blood Alcohol Testing Programs: Further data analysis and forensic implications." Forensic Science International, Vol. 178, Issue 2, pp. 83-92. July 4, 2008.
  • Yean-Kuen, Fang et al. "Integrated ethanol gas sensor and fabrication method thereof." U.S. patent 6,161,421. Dec. 19, 2000.