Aerosolization and dispersion of bacteria on hands by hand dryers during hand drying activities

Hand dryers are widely used in public space as an alternative to paper towels, yet their potential to release and disperse microorganisms in such space remain a public health concern. This study investigates the aerosolization and dispersion of bacteria on hands from two commercial hand dryers commonly used in public restrooms. A test chamber was built to simulate restroom conditions, and <i>Escherichia coli</i> K12 was used as a representative microorganism. Bacteria deposition on surfaces were assessed using agar plates in the test chamber. The release of airborne <i>E. coli</i> was quantified by collecting air samples in an confined space made by an Atmosbag. The results showed that the Excel Xlerator dispersed a significant number of bacteria near its air outlet and directly beneath. In contrast, the Dyson Airblade showed lower bacterial dispersion, with the highest colony number found on agar plates at the side of the hand dryer. Both hand dryers exhibited a decrease in bacterial colonies on agar plates that were placed at ground level as distance from the dryer increased. It is estimated that the Dyson Airblade released between 528 and 1000 colony forming unit (CFU) per drying activity, while the Excel Xlerator released 140 CFU per activity. While the potential for hand dryers to aerosolize bacteria from washed hands is low, the results highlight that hand dryers can disperse microorganisms to a considerable distance in the space. This study provides insight into the impact of hand dryers on indoor air quality and the spread of bacteria.