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How does a breathalyzer determine the alcohol level of the breath?

Modern tests for drunkenness, given by police to erratic drivers, use electronic breathalyzers. The person being tested blows into a tube. The breathalyzer has a platinum anode which causes the alcohol in the person's breath to oxidize into acetic acid. In the process, the alcohol molecules (particles made by the combination of two or more elements) lose electrons and initiate an electric current.

The more alcohol the breath contains, the stronger the current. If breath activates a green light on the breathalyzer, the driver is below the legal limit and has passed the test. An amber light means the alcohol level is near the limit; a red light means the level is above the limit.

Earlier breathalyzers measured alcohol levels using color-changing crystals. In the presence of alcohol, orange-yellow crystals (a mixture of sulfuric...

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