Jet-drying technology spreads infectious agents much further than paper towels, says a new study.
Using an air dryer might feel more sanitary than paper towels, because you don’t have to actually touch anything. But apparently that couldn’t be further from the truth.
A recent study in the Journal of Applied Microbiology has compared how viruses disperse from the hands of users of three different drying methods—paper towels, standard “warm air” dryers, and so-called “jet dryers” like the Dyson model.
Get Data Sheet, Fortune’s technology newsletter.
The lower-power warm air dryers spread contaminants further than paper towels, but the jet dryers were by far the worst culprits. They spread up to 190 times more of a noninfectious test virus used in the study than the other methods. The material was dispersed up to three meters away—nearly 10 feet—and a closer look at the study by Ars Technica found that about 70% of the dispersed material was at the height of a small child’s face.
Of course, in a perfect world, people would have thoroughly washed their hands before sticking them into the maw of a superpowered air jet—as Dyson has pointed out in response to previous similar findings. But we already know that more than half of us don’t bother washing our hands at all. And according to the CDC, effective handwashing takes about 20 seconds with warm water and soap.
Anything short of that—say, just a quick rinse—will leave things like norovirus and influenza virus on your hands. And viruses are hardy little things—the new study found virus in the air even 15 minutes after someone used a jet dryer, at levels 100 times higher than after a paper towel was used.
For more on health and technology, watch:
A previous preliminary study also suggested that air dryers leave more infectious material on the hands of users compared to paper towels.
Air dryers have generally been sold on their cost, convenience, and environmental benefits over paper towels. But in light of their findings, the study’s authors suggest that “the choice of hand-drying device should be considered carefully” in settings where infection is a particular concern, such as in hospitals and restaurants.