The researchers say that paper towels are the best way to reduce bacterial numbers when drying hands. Dr.Anna Snelling, one of the papers authors, says: "Good hand hygiene should include drying hands thoroughly and not just washing. The most hygienic method of drying hands is using paper towels or using a hand dryer which doesn't require rubbing your hands together".
No doubt this came as good news to the company that funded the research: Dyson Limited, who produce the Airblade, a dryer which uses air 'blades' to strip water from still hands. The paper found that the Airblade was "superior to the warm air dryers for reducing bacterial transfer."
The researchers quantified the effects of hand drying by measuring the number of bacteria on different parts of the hands before and after different drying methods. Volunteers were asked to wash their hands and place them onto contact plates which were then incubated to measure bacterial growth. The volunteers were then asked to dry their hands using either hand towels or one of three hand dryers, with or without rubbing their hands together, and levels of bacteria were re-measured.
However, the results also suggest that "if people use conventional warm air hand dryers for at least 30 seconds, then it is likely that the hygiene benefit will be similar to that achieved with 10 s use of the Dyson Airblade"
Expecting conventional dryers to function effectively using the reduced drying time for the Airblade is hardly reasonable. Obviously, if equipment is not used as designed, it will not function effectively.
Expecting the conventional dryers to work using a 10 second drying time, just because Dyson's latest gadget does is missing the point. When used for the recommended duration, the conventional dryers worked just as well as the new product.
When the A5 and Turbodry (the two conventional driers used in the study) were used for their recommended times of 30 and 35 seconds respectively, there was no significant difference in mean log bacterial count numbers compared to the that present when the Airblade was used for 10 seconds.
The work carried out at the University of Bradford also found that rubbing hands together while using traditional hand driers could actually increase bacterial numbers by bringing bacteria to the surface that usually reside within the skin. These bacteria can then be transferred to other surfaces.
However, this study used a drying time of 15 seconds for all dryers, significantly less than that recommended by the manufacturers of the conventional dryers.
What this paper has shown is that the Airblade does its job effectively in a relatively short duration of 10 seconds. But, what it also shows is that if you use a device incorrectly it won't work properly. That's hardly surprising, is it?
The paper is here.