The claim that an air dryer spreads more bacteria than a paper towel comes round again and again, sometimes on signs in the washroom. Except that the results in the literature . Here volunteers dried their hands both ways while instruments sampled the air. What came out?
Both methods, and barely above the room. Both produced a rise, and it was close to , similar to the rise caused by walking across the room and by the washing itself. The result does not prove every dryer is equal, and it is a reminder to ask about , who paid for the experiment and how it was run.
The claim that an air dryer spreads more bacteria than a paper towel appears in headlines as a fact, and different studies on the subject have reached opposite results.
In this experiment volunteers washed their hands and dried them with a towel or with a jet dryer, while instruments sampled the air and measured and bacterial concentrations in real time.
Both methods produced a rise, with no significant difference between them. And just as importantly: the rise was similar to the one caused by walking across the room and by the washing itself, which is to say close to the background level.
The caveats are part of the story here. The work was funded by a dryer manufacturer, one of the researchers worked there, and the sampling ran under limited experimental conditions, while other studies found an advantage for paper towels. A headline about the dirty method hides how far the result depends on the room, the device, the washing and the funding.
wat. Drying with a paper towel and with a jet dryer raised airborne bacteria to a similar degree, in work funded by a dryer manufacturer.
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A headline about “the dirty method” can hide how far the result depends on the room, the device, the washing and the funding.
How do we know?
The researchers measured particle sizes and airborne bacterial concentrations in real time before walking, washing and drying by both methods inside the same space.
What is still unknown
The work was funded by a dryer manufacturer, one of the researchers worked there, and the sampling was done under limited experimental conditions. Other studies found an advantage for paper towels.
Learn something?
Where to next
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Why do bacteria hold on better to a paper note than a plastic one?bacteria
Why has nobody fixed the splatter problem?hygiene