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New study says air hand dryers spread germs

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Jet air dryers 'spread bacteria from unclean hands'

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Germs are tiny organisms that are invisible to the naked eye. With the help of a microscope, scientists, doctors, laboratory technicians, and even you are able to view germs as they live, grow, and spread. We all know that after visiting the bathroom, we have to wash our hands and then dry them, either with a paper towel or a warm air hand dryer. Recently, scientists have discovered a scary fact about hand dryers. Hand dryers have been found to project, or fling, more germs into the air than whenever you use a paper towel. These hand dryers also project the germs farther within the bathroom than a paper towel does, meaning that the germs then stick to more surfaces such as doorknobs, counters, and even other people!

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How Germs Spread | Explaining the Science for Kids

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Over the past week or so, you might have read some alarming headlines about the cleanliness of jet air dryers, specifically Dyson's Airblade. "Using a Dyson hand dryer is like setting off a viral bomb in a bathroom," read one story. "Dyson Airblades 'spread germs 1,300 times more than paper towels'," said another. Dyson, understandably, isn't happy ("It's just not cricket," their in-house microbiologist told The Verge). But the argument over the cleanliness of different hand-drying methods is one that's been waged quietly for decades via studies, papers, and conferences. Getting to the bottom is a messy business.

There are a handful of major questions regarding the hygiene of jet air dryers like the Airblade: do they eject bacteria into the air during drying? Do they help remove bacteria from the hands? And are they any good at actually drying hands?
It's just not cricket
The recent study, published in the Journal of Applied Microbiology, looked at this first question primarily. It had test subjects dip their hands in a solution of bacteria, shake them (three times - no more, no less), and then use a variety of different hand drying methods. The researchers found that jet air dryers dispersed 60 times more bacteria into the air than warm dryers, and 1,300 times more than paper towels. Sounds pretty damning.

But, as Dyson points out, the test isn't entirely fair. It was conducted using gloved hands, making it easier to push off bacteria with air, and the bacterial solution was teeming - around 10 million infectious particles per milliliter. Speaking to The Verge, Dyson's in-house microbiologist Toby Saville called the study "fundamentally flawed," adding: "You'd be disappointed if an undergraduate had made some of these errors." He adds that the washing method (simply shaking the hands) was also insufficient.

It sounds a little like a setup. Even more so, says Saville, when you consider that one of the paper's authors, Keith Redway, has previously worked on a number of pro-paper-towel studies funded by the European Tissue Symposium (ETS) - an industry body dedicated to, yes, paper towels.
Redway says his study is about potential risk
Redway, though, stands by his science. Speaking to The Verge, he said that his study was all about "showing the potential for risk" with different types of hand drying. "It was a high level of contamination," he admits, "but that is possible if people don't wash their hands properly anyway, especially with pathogenic viruses." He adds that he asked his subjects to use gloves because the experiment might have posed a danger to them otherwise, and says that although this may have influenced the test, the fact that the conditions were the same for each drying method gives a clear idea of relative risk. Unfortunately, this is not a nuance that's conveyed in headlines like, "Dyson hand dryers spread thousands of germs."

Redway is more equivocal: "I've never condemned these jet air dryers or warm air dryers completely outright, but I don't think they should be in clinical or sensitive areas where cross infection is particularly important," he says. And other studies have supported the idea (quite logically) that jet dryers disperse more particles into the air than paper towels.

As for the funding, Redway admits that while he has received money from the ETS in the past, this particular study was independently funded. He says, "The only people I've never been asked to do work for is the warm air dryer people and the jet air dryer people, because they don't like what we come up with."

An infographic produced by the European Tissue Symposium based on Redway's research. (Image credit:

This caveating and counter-caveating also crops up when interrogating another measure of hygiene and hand-drying - the accumulation of bacteria on the hands during the drying process. Redway has been involved in reports showing more bacteria is left on the hands after drying with a jet air dryer than when using paper towels, but again, Dyson has objections.

A 2008 report by Redway commissioned by the ETS asked 20 test subjects to visit a public washroom. They then returned to a laboratory where their hands were tested for bacteria levels before and after washing and drying. The report says that those that dried their hands using paper towels reduced bacteria on the palms by between 32.8 and 85.2 percent, while those that used jet air dryers increased it by 9.1 percent to 82.2 percent. Again, it seems clear cut.

Saville's criticism is that the experiment didn't sample subjects' hands between washing and drying - only before and after. "When you're washing the hands, although you do wash bacteria off the surface, your skin is made up of lots of layers, and between each layers you've got another layers of bacteria," says Saville. "So what you do is you break up the skin, and the bacteria comes to the surface." He notes that the findings were only a report, and points to peer-reviewed studies that show no difference between the amount of bacteria left on the hands after different drying methods. (Though they don't include jet air dryers, just warm air dryers.)
bad blood has infected the hygiene debate
The problem seems to be that the debate has been overtaken by press spin and animosity. Although while talking to The Verge, Redway defends his work by saying it was only looking at an extreme case, when he's being quoted over at the European Tissue Symposium press site, the argument is reduced to "paper towels are great and jet air dryers are bad." Who's at fault here? It's difficult to say.

And Dyson isn't blameless either. Although Saville says - and I believe him - that all he wants is a level playing field, Dyson the company makes a point of touting the dryer's hygienic credentials, funding its own research that make paper towels seem like the unclean option. After Redway's recent study was published, Dyson even produced a video titled " Paper's dirty little secret," complete with a friendly but slightly menacing voiceover asking viewers: "Did you use a paper towel today? It wasn't as hygienic as you might think." Cue the CGI images of a paper tissue covered in little snot-like bacteria. The word Dyson used to describe Redway's study was "scaremongering," but that might cut both ways.

It doesn't help that there also seems to be bad blood between the opposing researchers. Redway describes Dyson as "quite an unpleasant company" and feels that they've been aggressive toward him, questioning his methods and credibility. Saville, meanwhile, says he's had little contact with Redway (they exchanged emails once but it didn't end well), but that he did once attend a conference incognito that the researcher was speaking at. Saville claims that Redway took the stage and ridiculed his research to the audience of pro-paper towelers. "It was pretty incendiary," he says. "He was whipping the crowd into a bit of a frenzy about it."

From an outsider's perspective it looks like animosity might have overtaken the science, and it's certainly true that the media hasn't helped, with sensationalist headlines raising the stakes for both sides. The thing is, if you know your research is going to be hammered into the crudest interpretation possible, then you have less incentive to be subtle yourself.
There's a germ of truth to both sides' argument
All of this seems self-defeating when you consider that Redway and Saville actually agree on what is perhaps the most fundamental and hygienically significant aspect of the Dyson Airblade: it's very good at drying your hands. Just as good as paper towels in fact. This sounds trivial, but it couldn't be more essential. Wet hands are magnets for bacteria. The moisture gives them a home, and if you touch dirty surfaces in a washroom with wet hands (like the door handle on your way out, for example), then bacteria is going to leap on board like it's a pool party.

"Drying is not about removing bacteria, that's not what it's there for. Washing is about removing bacteria," says Saville. "The drying step is just about drying, and the reason it's important is because if your hands are still damp, that moisture acts as a conduit for you to move bacteria [...] onto your skin."

On this point, the two sides are even willing to compliment each other. "The jet air dryer, surprisingly enough, is very effective at drying - as good as a towel," says Redway. Saville adds: "The paper towel is a hygienic way to dry the hands. We've never stepped too far away from that." And both sides agree that it's warm air dryers that are the bigger danger (the enemy of my enemy, you could say), as their heat and age often means they're home to bacteria themselves, and because they work more slowly, people are more likely to get bored mid-dry and walk off with wet hands.
Focusing too much on hand drying ignores the most important step: hand washing
All this discussion of drying, though, ignores one obvious, overwhelmingly important fact: it's washing your hands that's key when it comes to personal hygiene, and people just don't wash their hands enough. When you look at advice and research from agencies tasked with public health like the CDC and WHO, there's scant mention of drying techniques because getting people to wash is tricky enough. In a UK study, 99 percent of people visiting a public bathroom said they had washed their hands after going to the toilet. Recording devices showed that only 32 percent of men and 64 percent of women actually had.

Use proper soap, is the official advice, go through these six steps, and sing "Happy Birthday" twice before you even think of finishing up. Then - and only then - can we talk about drying.

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Dyson vs Big Paper Towel: the battle over hand-drying hygiene

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Over the past week or so, you might have read some alarming headlines about the cleanliness of jet air dryers, specifically Dyson's Airblade. "Using a Dyson hand dryer is like setting off a viral bomb in a bathroom," read one story. "Dyson Airblades 'spread germs 1,300 times more than paper towels'," said another.

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Several studies have found that air hand dryers can blow bacteria back onto your hands and spread germs more than paper towels. Real People Group/Getty Images

A new study indicates that using air hand dryers to dry your hands may spread germs more than paper towels.

Previous studies have also found that air hand dryers can blow bacteria from bathroom air back onto your hands.

Experts say that proper handwashing is still the most important action we can take to prevent transmitting COVID-19.

During the COVID-19 pandemic, many businesses have turned to touch-free methods to cut down on opportunities for spreading germs.

For example, many restaurants now provide a QR code for viewing their menu on your smartphone in lieu of traditional paper menus.

In addition, many business restrooms use hand dryers rather than paper towels.

However, according to a new study published in Infection Control & Hospital Epidemiology, the latter may not be as effective as we might think it is.

High-speed air dryers may actually leave more contamination on your hands than paper towels do.

In addition, they may spread germs onto your clothes, leading to more of them being transferred to other surfaces.

Dr. Paul S. Pottinger, a board certified physician and director of the Infectious Diseases & Tropical Medicine Clinic at the University of Washington Medical Center-Montlake, who was not involved in the new study, said the purpose of the new research was to attempt to understand whether different hand drying methods might affect the spread of germs in a hospital environment.

"To understand that, [the researchers] simulated contaminated hands by treating hands (either bare or gloved) with a harmless virus, then asked participants to dry their hands, either using paper towels or using an air dryer," Pottinger said.

They then detected the amount of virus that was transferred to various surfaces around the hospital.

When the researchers compared the two drying methods, they found that the people who dried their hands using the air dryer had spread more of the virus.

Unfortunately, we may not be able to apply the findings from this particular study in our battle against COVID-19.

According to Robert Smith, PhD, assistant professor in the department of biological sciences at Nova Southeastern University Halmos College of Arts and Sciences, there were several problems with the study.

"The amount [of the virus] that they put on is far above what one would reasonably expect to encounter in a normal environment. Thus, the study is likely overestimating how much virus is transferred to surfaces and remains on someone's hands," Smith said.

He pointed out that the study didn't control for handwashing procedure. What that means is that researchers didn't describe how participants washed their hands, nor did researchers ensure that everyone in the study was following the same procedure.

"Handwashing has been shown to be the single [most] effective way to cut down the transmission and spread of microbes, so this would be important to regulate in the study," he said.

He added that the study participants knew if they got the harmless virus on their hands or not. This could have biased them to behave differently for each treatment.

"The sample size is really, really small for a study like this. To have a change in the way that we think about handwashing, the study would have to be large and better planned out," Smith said.

But while the extreme conditions of this particular study may not be entirely applicable to real-world situations, previous studies have found that hot-air dryers can blow large amounts of spores from bathroom air directly onto your hands.

Essentially, air dryers may be bathing your hands in hefty doses of bacteria, including some that are typically found in feces.

As we try to navigate safely though the world during the COVID-19 pandemic, it may be best to avoid air dryers in public restrooms as an extra precaution.

However, it should be noted that studies have not found a direct link between the use of hand air dryers and contracting the coronavirus.

Pottinger said that the important thing is to wash our hands carefully using soap and water for at least 30 seconds.

"The way in which we choose to dry our hands is comparatively less important," Pottinger said. "But, as the study suggests, there may be benefit in choosing paper towel over electric hand dryer."

"In either case, the most important thing is to ensure that we prevent our freshly cleaned hands from coming into contact with contaminated surfaces, including a paper towel dispenser or a hand dryer," he explained.

Pottinger said he personally does choose paper towels, not only for the reasons indicated in the study, but because it allows him to grasp the restroom doorknob with the paper towel covering his hand to avoid contaminating it.

Smith agreed that properly washing your hands is the most important part of the process.

"It doesn't matter what you dry your hands with if there is bacteria and virus all over them because you didn't do a good job washing them in the first place," he said.

Smith added that the second best choice to handwashing is using a hand sanitizer with at least 60 percent alcohol.

He cautioned, however, that this method doesn't kill microbes as effectively as soap, water, and proper handwashing technique.

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Air Hand Dryers Can Spread More Germs Than Paper Towels

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A new study indicates that using air hand dryers to dry your hands may spread germs more than paper towels. Previous studies have also found that air hand dryers can blow bacteria from bathroom air back onto your hands. Experts say that proper handwashing is still the most important action we can take to prevent transmitting COVID-19.

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3rd Grade
3-LS4-3: Construct and support an argument with evidence that in a particular habitat some organisms can survive well, some survive less well, and some cannot survive at all.

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In this phenomenon, “warm air” hand dryers, an invention intended to make human life easier and to save trees, are found to spread more viral plaque-forming units and at a greater distance than the use of paper towels. Different types of dryers have also been found to project these viral units at different distances due to the amount of air flow they posses. In this phenomenon, students are faced with the problem of choosing the use of paper towels, which aren't environmentally friendly, or the use of warm air hand dryers, which aren't friendly to the human immune system.