A teenager from Canada has discovered through painstaking research that many of the hand dryers you find in public restrooms may be dangerously loud for children's ears.

The study by Nora Louise Keegan, 13, was published in the journal Pediatrics & Child Health. Her introduction notes that previous research found hand dryers may operate at levels that are dangerous even for adults, but that there was no research on the potential effects on children's more sensitive hearing. Keegan notes that Canadian regulations prohibit the sale of toys above 100 decibels.

"Sometimes after using hand dryers, my ears would start ringing and I also noticed that children would not want to use hand dryers and they would be covering their ears," Keegan told National Public Radio.

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Keegan used a decibel meter to test 44 hand dryers in public restrooms of places where kids frequent, such as schools, libraries, shopping and restaurants. She collected data over the course of 14 months, starting when she was nine years old.

To get a thorough sampling, she tested each dryer in 20 different ways. Each test involved a different combination of heights and distances from the wall, and with or without hands in the air stream. The heights included the average height of a 3-year-old child's ear canal and an adult man and woman's ear canal. The tests were also done when there was no background noise such as toilets flushing or people talking. 

Keegan found dryers made by Xlerator were the loudest. Her results showed all of them were above 100 decibels whenever hands were in the airstream. She also found several Dyson Airblade models were loud, with the loudest measurement at 121 decibels. Keegan provided links to each company's own manufacturing data in her assessment that the dryers ran louder than the companies claimed. 

The U.S. Environmental Protection Agency says 85 decibels is the level that can be dangerous for hearing.

Her research found that while some models operated at low sound levels, they were louder at a child's ear height than an adult's ear height. You can see a table of all Keegan's results at this link.

Keegan concludes that many hand dryers operate at sound levels above what the manufacturers claim and that those levels are dangerous to children's hearing. She also noted that older hand dryers that appeared to dry hands slower were quieter than newer ones that were louder but dried hands quicker.

Excel Dryer, the maker of Xlerator, released this statement.

"At Excel Dryer, we are committed to our customers. User experience is very important to us, which is why all our high-speed, energy-efficient models come with adjustable sound and speed controls as a standard feature. This allows facilities the ability to choose the best settings for their restroom environments."

Keegan has said Dyson has reached out to her to talk about her research, but NPR said she's been a little busy attending summer camp.

TEGNA has reached out to Dyson for comment.

Hand dryer
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