Testing for alcohol in the breath is common practice if, after administration of field sobriety tests, an officer still has due reason to believe that a driver is intoxicated. There are three main ways to test for alcohol in the breath: (1) portable breathalyzer, (2) intoxilyzer and (3) alcocensor. The most commonly used method to test for alcohol in the breath is the portable breathalyzer.

How the breathalyzer works

The breathalyzer is a portable device that measures blood alcohol concentration by estimating the amount of alcohol in the subject's breath through a chemical reaction. After receiving a 2- to 5-second breath sample through the mouthpiece the device spews out percentages that represent the total proportion of alcohol to blood in the body at that moment. There are several different chemicals inside the breathalyzer, but it is the potassium dichromate (a reddish-orange hue) that will change colors when in contact with the ethanol (morphing into varying shades of green). The outcome color represents a determinate level that corresponds directly with the BAC count (e.g., 0.04 might be a certain shade of aqua-green). Depending on how much alcohol is blown into the device, the color will vary, determining what level BAC the subject has. How does it work so fast? Silver nitrate acts as a catalyst to the potassium dichromate and ethanol reaction, pushing things along without altering the results. It's best to test 15 minutes after consumption for accurate results.

Other methods

In a similar but less portable fashion, the intoxilyzer also analyzes alcohol in breath. These devices are found commonly in police stations and are used upon a suspected drunk driver's arrival. When you breathe in, your breath enters a chamber. A beam of infrared light shines though the sample and the amount of absorption of waves directly corresponds to varying levels of alcohol, in a similar way that the varying shades of color in the breathalyzer test determine the amount of alcohol in the sample. Different amounts of alcohol are capable of absorbing different amounts of infrared waves. A mathematical equation further verifies the sample by making up for the difference between the "breathed" air sample and what level of alcohol would then be in the subject's "deep lung" air. Meanwhile, the alcocensor relies on fuel-cell technology to test for alcohol in the breath. As the subject breathes into the mouthpiece, the air again enters a chamber and the machine produces a linear graph which goes from zero to a peak, then back down to zero. The rate at which the output current peaks and falls determines the amount of alcohol in the sample.

Try this at home

Owning your own personal portable breathalyzer can prevent you from making poor decisions while under the influence. People are often unaware of their precise level of intoxification; a portable breathalyzer can give you a numerical reason not to get behind the wheel. Although every state in the U.S. has set the legal limit for driving at 0.08, most people begin to feel the effects of alcohol between BAC ranges of 0.03 percent and 0.059 percent. Check yours: portable breathalyzers are available online and at stores like Target from $5 to $500.

Source:

Breathalyzer.net

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