Grosser than ever, hot-air hand dryers spread fecal matter throughout buildings

Hands in hot-air hand dryer
Getty Images/Roberto Pangiarella

Think twice about using restroom hot-air hand dryers. The high-force air flow through dryer nozzles spreads all sorts of nasty particles, including tiny bits of poop light enough to travel through the air.

But the grossness doesn’t stop at your hands. In a study published in Applied and Environmental Microbiology, Connecticut researchers found bacteria dispersed by hot-air dryers spread throughout buildings.

The researchers tested bacteria dispersion in 36 University of Connecticut School of Medicine bathrooms. Rather than looking for feces flakes, the scientists searched for a harmless, lab-engineered bacteria called PS533. At the UConn school, spores of this strain of Bacillus subtilis are produced in a single basic science research lab.

University of Connecticut professor Peter Setlow, one of the study authors, told Newsweek the spores probably spread through the air. The research team found PS533 spores in all 36 bathrooms.

When the researchers installed high-efficiency particulate air (HEPA) filters to hand dryers, the collected spore amounts were reduced by 75 percent, but 25 percent still circulated.

The implications of the UConn research, not the first to call out hand dryer feces flow, are that surfaces in whole buildings can be contaminated by airborne matter, especially when pushed by high-force hand drying appliances.

It’s understandable forced-air hand dryers are used in public restrooms in the same room as toilets, adjacent to sinks. Employees at restaurants in many states are required by law to wash and dry their hands every time they use the restroom and before returning to food preparation or serving areas.

“Bacteria in bathrooms will come from feces, which can be aerosolized a bit when toilets, especially lidless toilets, are flushed,” Setlow told Newsweek. He added that microbes shed from the skin of the many people who travel in and out of public restrooms add to the contaminant mess in the air.

It doesn’t seem logical to position sinks and hand dryers outside bathrooms, perhaps in a separate room with a different ventilation system. Removing washup areas away from rooms with toilets could be a good idea, although it wouldn’t solve the whole problem.

The problem of bacteria air-dispersion lacks simple answers, but the University of Connecticut has taken a logical step: the UConn School of Medicine installed paper towel dispensers in the all of the bathrooms in the study.

Using paper towels when hot-air hand dyers are still available and in use means it will be less likely to have hot poo flakes blown directly on your wet hands after washing. As long as hot-air dryers are in use by others, however, nasty airborne particles can still cling to your clothes and spread throughout the building.

Updated on April 14: Added information about minimal gains from using paper towels if others still use hot-air dryers.

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