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Breathalyzers Aren't Accurate When Cops Use Hand Sanitizer

A small but telling new study casts doubt on current protocol.

by Paul Spencer
Dec 7 2016, 4:00pm

Photo: Chalabala/Getty Images

You might've heard that cough drops, or even a whiff of Listerine, can send a breathalyzer reeling—but now, even that trusty bottle of Purell is conspiring to get you off the road. 

Actually, you're not the problem here. It's in the hands—literally—of the people who administer the test, according to a small new study published this month in the American Journal of Infection Control. Ethanol-based hand sanitizers like Purell are typically required before administering a breathalyzer test, and researchers found that this action repeatedly skews results.

Breathalyzer machines detected alcohol on the tester's hands, which meant that sober people consistently registered as drunk. Surprisingly, researchers found the margin of error was huge. When testers used hand sanitizer and didn't let their hands dry, breathalyzer machines said a person was nearly two times above the legal alcohol limit. Worse, results could be skewed up to three minutes after the application of hand sanitizer.

Ten volunteers were tested for the study, using a machine called the Alco-Sensor III. First the administrators tested volunteers with unclean hands. Then they tested them again, after applying both foam and gel versions of hand sanitizer. The study aimed to determine whether or not time had an effect, too. When hand sanitizer was still present—as in, not completely dried off—the machines indicated alcohol in the sober person's breath. When testers tried wearing gloves, alcohol was still detected in a volunteer's breath up to one minute after the use of the sanitizer. 

Protocol, which typically requires testers to slather themselves with hand sanitizer, may be due for a change, concludes study author Beth Emerson, assistant professor of pediatrics at Yale. And not just for law enforcement: Hospitals also administer breathalyzer tests to quickly assess if a patient with an altered mental status is intoxicated. "This is typically confirmed with a blood test," Emerson says, "but that takes more time to come back."