What do you get when the hot-air hand dryer in a public bathroom blasts heat on your wet hands? Drier hands, yes—plus a handful of germs, including a species of bacteria that can often be found in feces.
That’s what researchers found in a recent study in which they exposed plates to the air in public bathrooms. Plates exposed for 20 minutes to bathroom air moved by a small fan became contaminated with an average 15 to 20 colonies of germs. But plates exposed to the hot air of a hand dryer for only 30 seconds came back with an average 18 to 60 colonies of germs.
Retrofitting the hand dryers with HEPA filters greatly reduced the number of germs blowing from the nozzles. But the researchers’ findings suggests that public bathroom hand dryers blow a lot more than hot air on your freshly cleaned hands.
The study was published in the journal Applied and Environmental Microbiology.