• air blade;
  • detection;
  • electric dryer;
  • enumeration;
  • food safety;
  • hand drying;
  • hand hygiene;
  • microbial contamination;
  • paper towels;
  • washroom contamination



This study compared the potential for cross contamination of the surrounding environment resulting from two different hand-drying methods: paper towels and the use of an air blade dryer.

Methods and results

One hundred volunteers for each method washed their hands and dried them using one of the two methods. Bacterial contamination of the surrounding environment was measured using settle plates placed on the floor in a grid pattern, air sampling and surface swabs. Both drying methods produced ballistic droplets in the immediate vicinity of the hand-drying process. The air blade dryer produced a larger number of droplets which were dispersed over a larger area. Settle plates showed increased microbial contamination in the grid squares which were affected by ballistic droplets. Using the settle plates counts, it was estimated that approx. 1·7 × 105 cfu more micro-organisms were left on the laboratory floor (total area approx. 17·15 m2) after 100 volunteers used an air blade dryer compared to when paper towels were used.


The two drying methods led to different patterns of ballistic droplets and levels of microbial contamination under heavy use conditions. Whilst the increase in microbial levels in the environment is not significant if only nonpathogenic micro-organisms are spread, it may increase the risk of pathogen contamination of the environment when pathogens are occasionally present on people's hands.

Significance and Impact of the Study

The study suggests that the risk of cross contamination from the washroom users to the environment and subsequent users should be considered when choosing a hand-drying method. The data could potentially give guidance following the selection of drying methods on implementing measures to minimise the risk of cross contamination.