Public restrooms can be a disgusting place filled with unflushed
toilets and other repulsive smells. The rise of hand-dryers is
only contributing to this problem, posing a more serious risk to
public health than most people think.
In 2018, researchers from the University of Connecticut suspected
that hand dryers in public bathrooms may be sucking up bacteria
from the surrounding air, and blowing it onto the freshly washed
hands of unaware guests. To prove this hypothesis, scientists
placed petri dishes in different locations around a bathroom, and
then recorded any mycobacterial growth. With the hand dryers off,
petri dishes exposed to the air in the bathroom grew one or zero
colonies of bacteria within a span of two minutes. However, petri
dishes exposed to the hot-air hand dryers for thirty seconds grew
anywhere from 18 to 254 colonies.