What's the Best Way to Dry Your Hands in the Age of COVID-19?

Three silver hand dryers on a teal tile wall


Aliaksandra Ivanova / EyeEm / Getty Images

Another way that the coronavirus is bad for the environment.

UPDATE: This post has been revised after receiving new information.
The debate over electric hand dryers has been going on probably since they were patented in 1922. So much hot air, and so many questions: Which is better for the environment? Which has a lower carbon footprint? Which does a better job? Which is more sanitary? Now with the coronavirus, the issue of tissue vs. hot air takes on new relevance.

Historically, TreeHugger stood with the trees.

From our very first look at the issue by Lifecycle Analysis expert Jenna Watson, it was clear that the electric dryer had a lower environmental impact. Jenna reviewed the data and concluded:

The use of paper towels has double the global warming burden of the hand dryer. I will probably keep drip drying my hands or wiping them on my pants, but in the event that I have to choose between paper towels or a hand dryer I'll pick the blowier, greener choice of the hand dryer.

She also noted that "one of the biggest keys to more sustainable products is greener and cleaner electricity sources." Many coal-fired plants have closed since she wrote that, tilting the balance even more in favour of the electric dryer. And that was also before Dyson invented the high velocity Airblade.

Dyson changes everything

The air blade doesn't dry hands by evaporating the water, like conventional hot air dryers. As Derek Markham described it, the high-velocity (430 MPH!) Airblade quickly scrapes the water from hands "like a windscreen wiper," and leaves hands completely dry afterward.

The company claims that their Airblade units use up to 80% less energy than conventional hand dryers, and can completely dry hands in just 12 seconds (compared to up to 43 seconds for other models), so these high-tech dryers could be not only helping to improve sanitation hygiene and public health, but also saving money and energy as well.

Dyson also claimed that the HEPA filter in the Airblade "can remove 99.97% of bacteria- and virus-sized particles from the air intake before the air is blown onto hands."

When architectural critic Mark Lamster complained about the Dyson Airblade, calling it "the most abhorrent work of design in recent memory" because of its noise and the electricity it used, sustainable design expert Yetsuh Frank tweeted a pointed response:

The paper towel industry fights back.

In response to the success of the Airblade, the totally impartial Kimberley-Clark, a big manufacturer of paper towels, commissioned a study that concluded that "jet air dryers increase bacteria on the hands by 42% and harbor bacteria and blow out bacteria by up to two meters." In addition, they say that "warm air dryers increase bacteria on the hands by 254%." Not surprisingly, they say that "paper towels are the most hygienic 'drying format' because they reduce bacteria by up to 77%".

Chart showing spread of viruses on hands
European Tissue Symposium

A study funded by the totally disinterested European Tissue Paper Association compared paper towels, warm air dryers (WAD) and the jazzy Dyson jet air dryers (JAD), and concluded that the Dysons spread 1,300 times as much bacteria into the air as using a paper towel. Study author Dr. Patrick Kimmitt said, “Our findings clearly indicate that single-use paper towels spread the lowest number of viruses of all the hand-drying methods we tested.” Study co-author concurred:

Our research and results over the years have revealed time and again that single-use towels are the safest way to dry one’s hands in the washroom. This virus study delivers further proof that when it comes to hygiene, drying one’s hands with a single-use paper towel is the safest way to reduce the spread of viruses after a visit to the washroom.

Dyson strongly disputes this, contacted TreeHugger after reading this post and according to Karen Holeyman, Lead Research Scientist and Microbiologist at Dyson,

Drying hands properly is an important step of proper hand washing as damp hands can spread up to 1,000x more bacteria than dry hands. Dyson AirbladeTM hand dryers are proven hygienic, and there is no scientific basis to suggest that our hand dryers spread pathogens or are less hygienic than paper towels. In addition, Dyson AirbladeTM hand dryers are the only hand dryers that have been globally certified hygienic by NSF P335 accreditation.

We have previously also shown this video from Dyson where they claim that their dryer is very different from the conventional ones.

Then the Coronavirus changes everything again. Or does it?

woman drying hands with a paper towel
Anthony Wallace / Getty Images

A recent research review by Julian Hunt and John Gammon looked at best practices in hospitals and research from around the world, and concluded:

Disposable paper towels offer the most hygienic method of hand drying. Indeed, warm air and jet air dryers are not recommended for use in hospitals and clinics for hygiene reasons. These types of hand dryers can increase the dispersion of particles and microorganisms into the air, contaminating the environment.

I had always thought old-fashioned roller towels would in fact be better (and not have any waste), but no: "Cloth roller towels are also not recommended as they become a general use towel when the roll comes to an end – and can be a source of pathogen transfer to clean hands."

The problem with Hunt and Gammon's review, as pointed out by James Marvin of Intelligent Facility Solutions Ltd (which makes hand dryers) is that it reviews all those studies that were paid for by the paper towel companies. As the authors say in their Limitations, "Scoping reviews are one step removed from the primary data, and therefore we rely on the authors’ reporting of results."

I have noted how frustrated I am at the University where I teach, writing "I also often leave bathrooms with damp hands because I do not have the patience for the old hot air dryers." But in James Marvin's long and interesting post Are Hand Dryers Hygienic? he makes an important point about the old hand dryers (like the one in the photo at the top)- they took a long time.

[The] argument was that hand dryers were ineffective and therefore the user didn’t tend to dry their hands completely. This again was true and wet hands have been demonstrated to carry more pathogens than dry hands, again another big plus for the paper towel industry.

However, the Dyson and other high velocity ones are different, relying on air speed instead of heat, and have been tested to a much higher standard. As Marvin points out,

You can see that modern hand dryers have come a long way from the warm air versions that the paper industry had a field day with. Hand dryers are now fast drying, environmentally friendly and help maintain cleaner facilities.

This post previously quoted a post in Wired, where the author talked to Peter Setlow, a biochemist at the University of Connecticut who contributed to the 2018 study Deposition of Bacteria and Bacterial Spores by Bathroom Hot-Air Hand Dryers Setlow told Wired: “Sorry, hand-dryer industry, my personal opinion is that they shouldn’t be used.” He then advised that he dries his hands on his pants. Meanwhile, Dyson points to another study, "finding that jet air dryers are the most effective method for removing contaminants, while using one’s clothing increased contaminant levels." A Dyson spokesperson told TreeHugger:

There is no reasonable scientific basis to suggest that such a method of drying one’s hands is a safer way to mitigate the spread of Covid-19. At this time when the public is understandably concerned about Covid-19, it is particularly dangerous to stoke fears about the use hand dryers that could lead the public to choose not to dry their hands at all in a public restroom and potentially increase the spread of germs.

The lesson in all of this for readers: wash your hands thoroughly, dry them carefully and thoroughly, and don't use your pants. And the lesson for writers: These are scary times; slow down and do more research.