Can Jet Hand Dryers Really Blast Out a Germ Cloud? Well, Yes and No

Hot Air Blower Dryer — What's the truth about those restroom hot air hand dryers? Are they more sanitary than paper towels, or are they blasting germ clouds out into the air? Wikimedia Commons (CC0 1.0)

The last thing people want in a public restroom is more germs, but depending on how they dry their hands, that may be exactly what they are spreading.

The latest in a vein of research studying the effects of hand-washing, hand dryers and germs shows that, in some cases, old-fashioned might be better.

In a study published Feb. 9, 2018, in the journal Applied and Environmental Microbiology, the authors found, after studying samples collected from both ambient bathroom air and blown bathroom air, that because hand dryers suck in the air in a restroom, which is full of constantly circulating microbes and debris, and then spew it out at high velocity, they actually expose people to more microbes.

The researchers exposed both types of air to petri dishes and found that when the hand dryers weren't running, only six bacterial colonies grew. But when the dryers were running, the total number of colonies grew to as many as 60 per plate, and included Staphylococcus aureus, which is capable of causing serious infection.

Just a Slight Breeze

Another study, published Nov. 30, 2015, in the Journal of Applied Microbiology compared different hand-drying methods and their effect on germ dispersal.

Researchers discovered that those deafening jet air dryers — touted by manufacturers for their cleanliness — can actually spread viruses across a distance of nearly 10 feet (3 meters). The jet air dryers are activated when a person vertically inserts their hands inside the machine, causing powerful air jets to turn on. However, researchers found that these air jets spread viral plaques, which are groups of clumped viruses, at a rate 1,300 times more than paper towels. The study did not investigate the distribution of bacteria, which are bigger than viruses.

The findings were recorded after participants dipped gloved hands into a solution that included an innocuous virus. Participants then shook excess liquid off their gloves and used one of three drying methods: paper towels, warm air dryers and jet dryers. Researchers then collected air samples at a variety of distances from each type of dryer. They also used petri dishes to collect viruses that landed on surfaces adjacent to the drying stations. In the end, the jet air dryer spread viruses the farthest.

The implications are significant, not only for people who cringe at the idea of making a public restroom "germier," but also for hospitals whose business is making people well.

Not so fast, says Dyson, the company makes the popular Airblade jet air dryers. In 2008, the Dyson jet air dryer was the first such product to earn accreditation from the Royal Society for Public Health. Dyson argues that 2015 research found that up to 88 percent of unused paper towels tested in the U.S. contain bacteria, which can transfer to hands.

Dyson also contends that the Journal of Applied Microbiology study artificially inflated germ concentrations. In a real-life situation, the company says, most people would not have the sheer number of viruses on their hands as was used in the study, nor would they stick their unwashed, virus-coated hands in a jet dryer without rinsing and cleaning first.

There Is Another Path

What's the best course of action for hand washers? Even the professionals are debating the issue. An April 2016 study published in Infection Control & Hospital Epidemiology compared the three-step handwashing method outlined by the U.S. Centers for Disease Control and Prevention (CDC) to the six-step strategy of the World Health Organization. The study, which observed doctors and nurses using both of these handwashing techniques, found the six-step method got rid of more bacteria. This method includes using an alcohol-based hand rub. The CDC has since changed their recommendation from the 3-step hand-washing process to a 5-step protocol.

The issue of compliance when implementing the six-step process came up during the study. "Only 65 percent of providers completed the entire hand hygiene process, despite participants having instructions on the technique in front of them and having their technique observed," says Jacqui Reilly, the study's lead author. "This warrants further investigation."

For those who still need to dry their hands as the debate rages on, the best bet may be a time-tested paper towel dispenser followed by liberal application of hand sanitizer. Oh, and don't forget to scrub with soap in the first place.