How Long Do Breathalyzers Detect Alcohol?

Written by J. Hirby and Fact Checked by The Law Dictionary Staff  

So you had a couple of drinks out with friends. You know you should not drink and drive impaired. How long must you wait before the breathalyzer will detect alcohol in your system?

"All Drinkers Vary in Metabolizing Alcohol"

Men and women vary in terms of how fast their bodies metabolize or processes alcohol. Weight, height, age and race are all factors for the drinker. The amount of food in your stomach is also an issue. Finally, the type of alcohol (wine, beer or liquor), rate of consumption and number of drinks consumed will determine how fast your body burns through alcohol.

"The Breathalyzer Measures Blood Alcohol Content (BAC)"

The breathalyzer device will measure the blood alcohol content in the breath you exhale. This is the easiest on-site method; urine or blood samples may be requested of you at the police station. The two primary types of breathalyzer technology used in hand-held devices are 1) electrochemical fuel cell or 2) semiconductor oxide sensors. Both measure the rate of oxidizing the alcohol. The infrared spectrophotometer breathalyzer equipment is larger and located in police stations.

Alcohol is either digested and metabolized by the body or excreted in sweat, urine or breath. On an empty stomach, the average man absorbs 20% of the alcohol straight into his bloodstream. Experts estimate that the average man will break down alcohol at the rate of 0.015 BAC per hour. Thus, if your BAC is 0.030, it would take 2 hours to have all the alcohol leave your system.

Some breathalyzers are faulty and will give you inaccurate readings due to body temperature, acid reflux or a bloody mouth. Natural compounds, like "ketones" can be mistaken for alcohol in the blood stream also.

"The Blood Test is the Most Reliable"

The courts remind you that drinking and driving is not illegal, "impaired driving" is illegal. But most states have made the BAC so low that this is a distinction without a difference. Usually, a police officer will take an "impaired driver" to the police station to prevent him from driving, book him and get a more reliable blood test.

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