How Breathalyzers Work

Drivers who can pass roadside sobriety tests -- by touching their noses or walking a straight line -- may still be over the legal limit for blood alcohol and be a hazard on the road. Breathalyzers help police find out who's really driving drunk.

Many officers in the field rely on breath alcohol testing devices (Breathalyzer is one type) to determine the blood alcohol concentration (BAC) in… » Full Story on HowStuffWorks