Tag Archives: dyson
It’s all in the friction: Hand dryers are germ-flinging BS
The benefits of paper towels versus conventional blow dryers for drying after handwashing are well-documented.
But what about those high-tech – and expensive – Dyson thingies that seem to be popping up everywhere.
I say, show me the data.
Caroline Weinberg writes that a study published in the Journal of Applied Microbiology showed that Dyson jet air dryers can fling germs as far as 10 feet from the device.
For the experiment, researchers dipped their gloved hands in a suspension of the bacteriophage MS2 (similar in structure to the contagious enteric viruses transmitted in poop). The hands were then dried by one of three methods. First up were Dyson jet air dryers, which are designed to push water off of your hands in 10 seconds with roughly the force of a jet engine. Next were warm air dryers, which blow warm air downwards and supposedly remove water via evaporation. The final competitor was paper towels, which use absorbent paper to remove water from your hands (and actually leave them dry).
The first part of the experiment looked at how many bacteria are blown back on you during the drying process. Researchers erected a vertical board roughly 16 inches away from each dryer and counted the viral particles that landed on it. Overall, the jet dryer dispersed 60 times more particles than the warm air dryer and 1,300 more than the paper towel. 70 percent of particles hit the board between 2.5 and 4.5 feet—roughly chest or stomach level on an woman of average height, or right at the face level of a small child. At the highest density point, the jet air dryer dispersed 167 times as many viral particles as the warm air dryer and 8,340 times as many as a paper towel.
For the second part of the experiment, researchers studied air dispersal, or how much of the bacteria is spread into the air around the machine or towel. Airborne virus counts were consistently higher around the jet dryer both over time and distance. The jet dryer dryer propelled the virus as far as 10 feet away, with high levels recorded a full 15 minutes after use. There was no significant difference in air dispersal between warm air dryers and paper towels.
This isn’t a perfect study: Because it was done in a lab setting, researchers could not account for individual behaviors or real world differences. They also only tested one example of each hand drying device (Dyson is taking the heat here, but they are not the only makers of jet air dryers) and did so over a small number of trials. Critics of the study also rightfully point out that most people don’t dip their hands in bacteria prior to using the hand dryers: they wash their hands first. And it’s true that if one were to stick perfectly clean hands into a dryer, there would not be germs to blow around.
Unfortunately, here in the real world, 95% of people using public restrooms fail to adequately wash their hands. Sure, a small percentage may use the scientifically vetted, 42-second-long, six-step hand washing process that most effectively rids your hands of all the filthy germs you’ve picked up in the bathroom and world at large. The rest of them (OK, us) are doing a quick scrub or, worse, simply passing their hands under a running faucet for a few seconds for the illusion of cleanliness. So while the hands most people place in the dryer aren’t drenched in germs, they are likely carrying, among other things, poop particles. Poop particles that the machine then proceeds to blow all over the room, including back on the very hands you just cleaned.
This isn’t the first time a study has suggested that hand dryers are germ cannons, either. A 2014 study published in the Journal of Hospital Infection also supports this finding—but it was dismissed by Dyson as funded by Big Paper Towel (in their defense, that study was literally funded by Big Paper Towel, i.e. the European Tissue Symposium,). Dyson would direct us, instead, to 2011 study published in the Journal of Applied Microbiology that found their air dryers to be more effective at preventing the spread of germs than warm air dryers. Now it was Big Paper Towel’s turn to cry foul—that study was funded by Dyson Limited. The current study in question is funded independently by the researchers’ university (though the lead author has worked with the European Tissue Symposium in the past) lending it a hopefully uncontaminated air of legitimacy.
A few months ago, shortly after this study was published, Dyson posted an ominously narrated attack ad of sorts titled “Paper’s Dirty Secret.” Don’t listen to Big Jet Dryer’s propaganda (well, maybe listen to it, because the video is hilarious—but don’t believe it). It is true that a 2012 pilot study found unused paper towels to be contaminated with small amounts of bacteria. But paper towels have been repeatedly shown to be efficient, effective, and—perhaps most importantly—not responsible for flinging extra poop germs through the air.