Bad Designs? Hot Air-Dryers Suck Up Poo-Particles and Spray Them All Over You

Many hand-dryers in bathrooms can undo all your hygienic work and increase your chances of getting sick.
Kashyap Vyas
The photo credit line may appear like thisDwight Burdette/Wikimedia Commons

Washing your hands after using the restroom is the best way to keep yourself, and people around you, clean and hygienic. This is because infectious viruses and bacteria found in the restroom can be easily transferred from one person to another with just a simple touch.

However, once you clean your hands, the hot air-dryers, which are most common in bathrooms these days, can reverse that hygienic effort you’ve put to clean your hands.

A study conducted at the University of Connecticut found that hand-dryers sucked in the pathogens from the surrounding area and sprayed them back all over, well, everything. The findings are in line with previous investigations, showing that jet-dryers can spread viruses and other germs from hands into the air.

While the previous studies were claimed to be funded by the paper towel industry, which raised questions about the accuracy and bias, this new study lends more authority to the claims. Notably, it demonstrates that even low-powered hand-dryers can spread infectious microbes already present in the surroundings.

When you flush the toilet that doesn’t have a lid, the turbulence it causes throws the bacteria into the air, where they continue to swirl. Once the dryer is switched on, these microbes are sucked through the intake and are then heated and sprayed back onto your moist hands and other habitable surfaces.

The critical research took place in the bathrooms of the research facility at the University of Connecticut. In one case, the researchers placed plates of agar media (gelled bacteria food) for two minutes in bathrooms with dryers off. In another case, the bacteria were blasted with dryer air for 30 seconds, keeping them at 12 inches away from the nozzle.

In the case where bathrooms were still, they caught zero to one bacterial landing per plate. While the same plates collected 18 to 60 bacteria when the blowers were turned on for 30 seconds.

However, the is some hope! The germ count was significantly reduced by retrofitting the dryers with HEPA filters.

The final test involved studying the possibility of other bacteria the dryers were blowing out. The researchers found that with or without HEPA filters, the blowers excited potentially infectious microbes including Staphylococcus aureus, a bacterium that can cause a range of illnesses.

The researchers believe that one reason hand dryers may disperse so much bacteria is due to volume. A large amount of air passes through hand dryers, 19,000 linear feet/min at the nozzle. "The convection generated by high airflow below the hand dryer nozzles could also draw in room air,” they said.

The study took place in bathrooms near the lab studying the spore-forming bacterium Bacillus Subtilis strain PS533, which is although harmless but has a unique resistance to antibiotic kanamycin. Researchers found that the air dryers were also spreading the spores of PS533, and were able to survive from rest of the germs collected from the toilet in the presence of kanamycin.

PS533 “was almost certainly dispersed throughout bathrooms in the research areas as spores, which would easily survive desiccation in room air, as well as the elevated temperatures in hand dryer air; however, growing or stationary-phase bacteria would not be nearly so hardy as spores,” the authors said. “However, the facile dispersion of one bacterial strain throughout a research facility should probably be a concern to risk assessors and risk managers when dispersion of potentially pathogenic bacteria is considered.”

The study is indeed a wake-up call, especially for the authorities responsible for keeping the research and clinical settings hygienic.


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