Washing your hands after using the washroom is an essential part of daily hand hygiene. However, washing alone is not enough. Hands should be carefully dried after cleaning as studies show that wet hands can carry a considerable amount of germs. 10 seconds already play a decisive role here. In just 10 seconds of drying hands with paper towel 99.8% of the bacteria are removed.
In public washrooms, one often finds electronically operated hand dryers instead of paper towels. The devices are divided into 2 types. With the JET Stream dryers, the hands are held into the device for drying. An air stream (up to 600kmh fast) is generated by a vacuum that sucks in air from the washroom. As a result the water is blown from the hands to dry them and residual moisture evaporates. The second type of air dryer is the hot air blowers, which are also electrically driven. They also use a vacuum to suck in air which is then heated and eventually evaporates the water on the hands.
Many users ask themselves whether JET stream dryers and hot air blowers spread more germs than they eliminate.
British scientists have investigated the devices.
“I haven’t used an electric hand dryer in 20 years – since I started my research in the field.” The clear statement comes from Keith Redway, a microbiologist at the University of Westminster in London. He has studied how hand dryers spread bacteria and viruses. He doesn’t give good marks for the various electrical devices.
Jet dryers are particularly problematic.
In one of his experiments, people first immersed their hands in a liquid enriched with viruses, protected by gloves, and then dried them. Trials were conducted with users drying their hands with paper towels, with a warm air dryer and with a jet stream dryer. Redway and his team then investigated how many viruses they were able to detect in the room.
It was noticeable that the jet dryers distributed a particularly large number of viruses in the room, says Redway. “In fact, it was 1300 times as many virus particles compared to paper towels. And it was over 60 times as many as warm air hand dryers.” The reason is that some jet devices eject particles from the side. They can then hit bystanders. That’s what worried the researchers, Redway says. “This could be the face height of a little child standing next to his parents while they’re using the dryer.”
What conclusions can be drawn from the results?
“Every microbiologist knows that moving air can spread pollution and increase the risk of infection,” says Redway. However, the researchers do not say that warm air dryers are extremely dangerous and should be banned. But paper towels pose the least risk of contamination to air and the environment. Hand drying with paper towels is also the most popular drying method of all washroom visitors. A study by the INTERMETRA Business & Market Research Group shows that 62% of all users prefer paper towels to other ways of drying their hands.
In summary, any type of hand drying is better than leaving your hands wet. However, the Commission for Hospital Hygiene and Infection Prevention (KRINKO) recommends the use of disposable paper towels due to the degree of drying and user-friendliness. In some areas the use of electrical appliances is not recommended. This applies above all to hospitals but also to the food industry, schools and old people’s homes.
Patrick et al. residual moisture determines the level of touch-contact-associated bacterial transfer following hand washing
Best et al. Microbiological comparison of hand-drying methods: the potential for contamination of the environment, user, and bystander. Journal Hospital Infection (2014)
INTERMETRA Business & Market Research Group. Study of the consumers’ attitudes to different handdrying systems for European Tissue Symposium (2008)