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Reading between the lines

September 21, 2010

ResearchBlogging.orgHave you ever used one of those Dyson Airblade hand driers? I’ve used them at SFO and even in some restaurant bathrooms, and I have to admit, they’re pretty neat.

Whether or not they’re actually better at drying your hands may be an open question, but  according to research published in the Journal of Applied Microbiology, it may be (marginally) better at removing bacteria:

Conclusions: Effective hand drying is important for reducing transfer of commensals or remaining contaminants to surfaces. Rubbing hands during warm air drying can counteract the reduction in bacterial numbers accrued during handwashing.

Significance and Impact of the Study: The Airblade™ was superior to the warm air dryers for reducing bacterial transfer. Its short, 10 s drying time should encourage greater compliance with hand drying and thus help reduce the spread of infectious agents via hands.

I’m going to be honest – I’m no expert in hand-drying technology, but this report seems a bit… um… crappy. First, one of the authors is from Dyson’s microbiology group (they have a division of microbiology?!?) – the other two are from a university, but at first I had a bit of trouble with the possible conflicts of interest. Then I looked at the data. I feel like it exonerates them from any claims of shillery – If I were going to fake science for money, I feel like I could do a better job. I definitely believe the data, I just think their stated conclusions are a bit overblown.

Basically, they had people handle meat to contaminate their hands, then wash their hands, then dry their hands in one of several ways, and measured how much bacteria was on their hands. The results are laughable.

Using the Dyson drier was marginally better – it’s statistically significant (which means there’s a less than 5% probability that the difference observed is due to chance), but if the difference is between 300 and 200 CFU’s, I don’t think it’s actually functionally significant. Besides that, using a paper towel was actually quite a bit better than any of the hand driers.

Anyway, I don’t know why I spent an hour of my life reading and writing about hand driers and bacteria. But when an add says “[product x] has been scientifically proven to [wondrous action],” I’ve always wondered where that research comes from. Now I know.

Snelling, A., Saville, T., Stevens, D., & Beggs, C. (2010). ORIGINAL ARTICLE: Comparative evaluation of the hygienic efficacy of an ultra-rapid hand dryer vs conventional warm air hand dryers Journal of Applied Microbiology DOI: 10.1111/j.1365-2672.2010.04838.x

7 Comments leave one →
  1. James permalink
    September 21, 2010 2:37 am

    I used these in Melbourne Airport and they were awesome. Is it weird to be impressed by a hand dryer?

  2. Kevin permalink*
    September 21, 2010 2:37 pm

    If it’s weird, I don’t want to be normal.

  3. Rachel permalink
    September 22, 2010 11:30 pm

    But bacteria is less the point… they need a study to show how much coolness is left on you after drying your hands. I’m pretty sure paper towels wipe away coolness, and I would not be surprised to hear that an airblade actually raises your coolness by a statistically significant amount.

    • Kevin permalink*
      September 22, 2010 11:43 pm

      You make an important point.Unfortunately, there are no good reagents to accurately quantify coolness, so that important study is not currently feasible.

  4. September 26, 2010 9:07 pm

    I love the idea of dyson having a microbiology department, although I imagine working there would mostly involve making graphs for the “this product removes 99% known germs!” commercials.

    I have an embarrassing story to tell: the first time I saw one of those airblade dryers I had no idea how to use it. I was staring at it, baffled for a while, before cautiously inserting my hands into the empty space. Jumped a little when the air suddenly came out. 😀

    • Kevin permalink*
      September 27, 2010 3:51 pm

      Thankfully, the first one I used had detailed pictographic instructions. If it hadn’t, I doubt I would have even realized it was a hand-dryer.

  5. Brett permalink
    August 2, 2011 3:33 am

    I’ve been told those tests are done in sterile conditions. But then they’re installed in public toilets. The air quality would be slightly different in a smelly bathroom, I’m guessing.
    Just a thought.

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