Bioaerosol Formation and Bacterial Transfer from Commercial Automatic Hand Dryers

Three experiments were conducted to determine to what degree hand dryers transfer bacteria. All hand dryers in public locations tested displayed transfer of aerobic microorganisms with an average transfer of 58 CFU/cycle ranging from 2-238 CFU/cycle.

The 2nd experiment found the commercial hand dryer with higher exit air velocity had a greater bacterial transfer rate than the commercial brand tested with a lower air flow exit velocity. The 3rd experiment revealed that hand dryers can spread aerosolized bacteria at least 90 cm from the air exit and that foods with a rough surface such as strawberries collect significantly more microorganisms (170,000 CFU/cycle) from hand dryers compared to foods with smooth surfaces such as grapes.

Overall, the series of experiments show that hand dryers aerosolize and spread microorganisms and the source of the microorganisms can be from the air in the environment immediately surrounding the dryer and from microorganisms residing on the outlet nozzle.

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