Breath analyzer: How does it function?

Breath analyzers are used by the traffic policemen in order to find out if the driver of the vehicle has consumed alcohol. This test is done on the spot to find out the blood alcohol concentration (BAC).

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When alcohol is consumed, it enters the blood stream of the body. As the blood enters the lungs, alcohol being a volatile substance vaporizes from blood. The vapor moves across the air sacs of the lungs called alveoli into the air which is exhaled. Different countries have different range of BAC set as a standard. In India, if BAC is more than 0.03 grams (that is 30mg/100ml of blood), the driver can be punished by law. 
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There are three types of breath analyzers – Breath analyzer, intoxilyzer, alcosensor that detect alcohol concentration in various ways. A breath analyzer uses chemical reactions to determine BAC while intoxilyzers use Infrared rays and alcosensors use chemical reaction of alcohol inside an energy conversion device called fuel cell. Apart from these three types, there is also an iBreath Alcohol Breath analyzer which is a little handy device that could be plugged into the base of an iphone or ipad.

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The major ingredient found in all alcoholic beverages is ethanol (ethyl alcohol). The breathalyzer method determines alcohol levels by monitoring a chemical reaction that occurs in the presence of alcohol. Alcosensors monitor chemical reactions within a fuel cell to take alcohol content. When a person breathes into a breath analyzer, ethanol present in the breath gets oxidized to acetic acid. Along with acetic acid, two protons and two electrons are also produced. There are two platinum electrodes with a porous acid-electrolyte material sandwiched between them inside the energy conversion device. A wire is connected to an electrical current meter from the electrode. When breath is exhaled, the two electrons produced due to the chemical reaction, cause flow of electric current through the wire. A microprocessor measures the current and calculates the BAC.

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