This Is How Hand Dryers Spread Bacteria

This Is How Hand Dryers Spread Bacteria

If you’ve ever had the sneaking suspicion that hand dryers in public bathrooms just spray bacteria into the air, then you’ll want to look at this spatterful photo. A trio of scientists set out to test exactly how hand dryers aerosolise bacteria, and the results are gross.

The study from August, brought to our recent attention by Jesse Singal at Science of Us, began with paint. Volunteers coated their hands in paint and dried them with paper towels, a warm-air dryer or a jet dryer to visualise how droplets are dispersed. That Jackson Pollack you see up above is the work of a warm-air dryer.

The researchers then coated volunteers’ hands in lactobacilli bacteria to simulate the dirty hands of someone who did not wash properly. Air samples revealed that jet dryers, which put out forceful blasts of air, were the worst offenders. Gentler warm-air dryers fared slightly better, and paper towels, of course, did not do spew out much bacteria at all. To a number on it, using jet dryers led to 27 times as much bacteria in the air than using paper towers.

Now, presumably, none of this would matter if our hands were already clean when we went to dry them. Reminder: you’re probably washing your hands wrong. [Science of Us, Journal of Hospital Infection]

Pictures: Journal of Hospital Infection, Littlestocker/shutterstock, Juergen Faelchle/shutterstock. Photoillustration by Andrew Liszewski

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