Electric Hand Dryers as a Source of Bacterial Contamination

Abstract

The most effective way to prevent disease is through hand washing, which includes the following four steps: using warm water, using soap and friction, rinsing and finally drying. Studies have shown that the ambient air within washrooms can contain bioaerosols which are released into the air through toilet spray, sneezing and coughing. Dryers have been found to be able to transmit these bacteria from the ambient air through to the exhaust air. If this were true, the electric hand driers could be a potential source for bacterial disease transmission. As a result the general public could be at risk of acquiring infectious diseases from electric hand dryers found within these washrooms. The purpose of this study was to demonstrate that the concentration of bacteria in the exhaust air of electric hand dryers was greater than that of the ambient air of the washroom. Sampling was done in 30 female washrooms selected randomly from the same facility. From each washroom 2 samples were taken, one from the hand dryer at the opening of the nozzle and one from the ambient air measured in the centre of the washroom. Samples were taken using settling plates for the dryer and a RCS for the ambient air, both containing nutrient agar. Bacterial counts for each sample were enumerated 48 hours after sampling. Results showed a decrease in bacterial counts in air from the hand dryers when compared to the ambient air. This significant difference (p < 0.05) suggests electric hand dryers are beneficial in reducing bacteria numbers found in the air. These electric hand dryers are capable of decreasing the bacterial concentrations found in the ambient air before passing over drying hands. Decreased bacterial concentrations in exhaust air of these dryers can lead to decreased bacterial recontamination of an individual's hands, potentially decreasing disease transmission rates.