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Hand drying and hygiene

The November 1997 issue of Food Safety & Hygiene contained an item on hand drying and hygiene. A recommendation that a re-appraisal of the use of hot air dryers in toilet areas used by workers in food operations was included.

In response to that recommendation, the Australian agent for World Dryer Corporation has supplied us with a report prepared by a respected food research laboratory in the United Kingdom. The title of the report is The Evaluation of the Performance of World Warm Air Hand Driers. The evaluation was designed to answer a number of questions in relation to the driers and the critical one in our discussion is: do hands have more or less microbes on their surfaces after drying with warm air hand driers compared with paper towels?

The report concludes, "provided that the hands were dried properly using the full cycle (30 seconds) of the World warm air hand drier, results achieved were similar to those obtained when drying hands properly using paper towels".

Our comment in the November issue of Food Safety & Hygiene cited two reports, one from the UK and one from France. It is not the aim of this Bulletin to report scientific studies in detail. However we noted that the French report concluded that bacterial levels on hands after hot air drying could remain high because moist hands provide a reservoir of soil and push buttons on dryers are often heavily contaminated. A 20 second drying cycle was used in this study. More directly comparable with the World dryer report is the other UK study discussed in November.

This study concluded that bacterial counts on the hands may increase after standard washing and hot air drying and went on to say that those published studies, cited as references, which show little difference in hygiene with hand drying methods didn't measure normal washing and drying habits and conditions. The authors reported that in their study:

• the majority of people (53 subjects) are too impatient to use hot air dryers for long enough to ensure adequate dryness. Even with a drying cycle set to last 30 seconds, men on average leave after about 20 seconds (55% dryness achieved), women after about 25 seconds (68% dryness achieved).
• many more people (about 40 per cent) using hot air dryers subsequently wipe their hands dry on clothes etc.

It is clear that the varying performance reported for hot air dryers is closely related to the drying time. The fact that a hot air drier may be set on a 30 second or greater cycle does not mean that people will dry their hands for 30 seconds. Standard 4.2 of proposed national food hygiene legislation will require a food handler after washing his or her hands to 'dry his or her hands on a single use towel or in a way that is not likely to transfer pathogenic micro-organisms to the hands'. Proper training in hand washing and drying procedures will be an important part of food hygiene training and this should include an appraisal of just how these procedures are carried out.

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Prepared by Keith Richardson and Beverley George
Food Science Australia
PO Box 52, North Ryde 1670. Tel +61 2 9490 8397 Fax +61 2 9490 8499
Email enquiries@csiro.au