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Chairman of the ETS, to get their side of the story, and he assured me that the study wasn’t ‘targeted’ in any way. Instead, he said: “It was considered extremely important that Professor Wilcox was free to do the study.


“We approached him to say we were interested in comparing the aerosolisation of microorganisms with different hand drying systems. There was no direct involvement from the ETS in the experiment, so there’s no way that we influenced it.”


The study was divided up into two separate parts, the first of which saw participants put paint on their hands and then use the three different drying methods to see where the paint ended up, designed to show the visible spread of water in the drying process. During the second part of the study, participants wore gloves that were contaminated with bacteria not normally found in the washroom, in this instance lactobaccili, ‘to simulate poorly washed, contaminated hands’. They then dried their hands using the three different methods, and air samples were collected throughout the washroom to determine the spread of these transient bacteria. These samples were taken at various time intervals to try and see how long the bacteria remained in the air after drying.


What the study then found was that air bacterial counts in close proximity to the hand dryers were 4.5 times higher for the jet air dryers than warm air dryers, and 27 times higher when compared to paper towels. A similar pattern was also found for bacterial counts a metre away from the dryers. Professor Wilcox then concluded that “Jet air and warm air dryers result in increased bacterial aerosolisation when drying hands. These results suggest that air dryers may be unsuitable for use in healthcare settings, as they may facilitate microbial cross-contamination via airborne dissemination to the environment or bathroom visitors.”


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Although the conclusion seems fairly set in stone in terms of what they found, Dyson’s Toby Saville felt that it was unfair to generalise the results because of a flawed methodology that, he believes, “doesn’t represent reality in any way, shape or form.” One of the main points of criticism from him was that tens of millions of bacteria were used when contaminating the gloved hands.


He said: “I’ve done a lot of sampling on people’s hands over the years, and you don’t get tens of millions of bacteria on your hands that you can remove, not even your own bacteria. Unless you are the messiest toilet visitor I’ve ever seen, you don’t get that much transient bacteria, it just doesn’t happen.”


Toby also felt it was important to factor in the level of bacteria already present in the washroom before drying takes place, referencing some studies that Dyson had carried out themselves with the Campden & Chorleywood Food Research Association. He said: “They basically showed that using an Airblade, using paper towels, using another hand dryer, in the context of what was in the air anyway, it was completely insignificant, and it doesn’t matter at


all. There are bacteria in the air all the time, we breathe them in every second, they just don’t harm you in those kinds of levels.”


But, because the study was focussing particularly on infection control, especially in hospital environments, the ETS feel that the high inoculant count was justified and necessary to highlight the potential risks that one might face.


Roberto Berardi added: “It should be pointed out that when somebody visits the toilet and gets contaminated with faecal material, human faeces has literally ten billion bacteria per gram. And if you’ve got somebody in there with norovirus – it’s a very small amount of norovirus that can cause an infection, often less than 100 colony forming units. So if you think of a hospital environment, if you’ve got a visitor going into a public washroom, using an electric dryer, getting contaminated with norovirus and then going to see a patient with poor immunity, I think it is an issue.”


The ETS were also keen to stress that, contrary to what Dyson and other hand dryer manufacturers may think, their study wasn’t intended as an attack; instead it was more a case of “putting everything into perspective.”


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