Warm air hand dryers increase bacteria on hands

Tuesday, 21 April, 2009

Warm air hand dryers cause an average 254% increase in the number of bacteria on the palms of people’s hands as well as contaminating the surrounding area, according to a recent study by University of Westminster in London.

The study also showed that, on average, paper towels reduce bacteria on the hands by 77%.

The University’s School of Biosciences conducted a study of three different hand drying methods — paper towels, regular warm air dryers and the new-generation ‘jet’ air dryers. Each drying option produced radically different results with warm air hand dryers causing an increase in the amount of bacteria found on palms and finger pads.

Warm air hand dryers result in largest bacteria increase

Regular warm air hand dryers performed by far the worst in the tests with an average bacterial increase of 194% on the finger pads and 254% on the palms. The results suggest an increase in the amount of Staphylococcus aureus, a bacteria known to cause food poisoning and potentially penicillin-resistant infections.

University of Westminster senior academic Keith Redway said: “The presence of any type of Staphylococcus aureus on the hands of a worker in the food industry or medical field should be taken seriously as should any increase in its numbers caused by particular hand drying methods.”

Airborne bacteria

The study also tested the new type of ‘jet’ air hand dryer. These air hand dryers increased bacteria by an average 42% on the finger pads and 15% on the palms. The air dryers do not only cause an increase of bacteria, they also contaminated the washroom environment and other washroom users. This is caused by the high airspeeds of up to 640 km/h that blow out of the unit. Tests showed that bacteria can spread as far as 2 m from the jet air dryer while regular warm air hand dryers spread bacteria 0.25 m.

“The superior performance of paper towels over the two types of dryer in reducing the numbers of bacteria was shown with both the finger pads and the palms of the subjects,” said Keith.

Paper towels are the safest method

The test confirmed that paper towels are the safest method of drying your hands after washing. In all tests, paper showed a reduction of bacteria. The average decrease was 76% on the finger pads and 77% on the palms. Also, paper is not likely to contaminate the washroom environment or other users.

“Using paper towels results in a significant decrease in the numbers of bacteria on the hands, a clear advantage compared with the increases observed for both types of electric hand dryer tested in this study. In addition, paper towels are far less likely to contaminate other washroom users and the washroom environment,” said Keith.

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