Scientists have found that drying hands with jet air dryers produces more aerosols than when drying them with paper hand towels. Contamination of hand dryer users by splattering was found to be 10-fold higher when using jet air dryers than when using paper towels, and contamination of other washroom users was also significantly greater.
The results have major implications for hygiene in public washrooms. Hand drying is an essential step in ensuring optimal hand hygiene. It helps to remove microbes remaining on hands following poor handwashing and so reduce the spread of infection in the community.
The study was carried out earlier this year by a team at the Leeds Institute of Medical Research of the University of Leeds, UK & the Department of Microbiology of Leeds Teaching Hospitals NHS Trust, UK. Participants dried hands using either a jet air dryer or paper towels and wore face masks as a way of measuring the risk of inhaling viruses.
Mask contamination by splattering and droplet deposition was investigated up to 15 min following each procedure.
A bacteriophage (a type of virus) was added to volunteers’ hands before they dried these in order to investigate whether microbes on poorly washed hands can spread across the washroom.  Contamination of the facemask of the person drying their hands and of the mask of another individual in the washroom at 1 meter and 2 meter distance, were measured. Volunteers waited for 15 minutes post-hand drying to examine whether air droplets continued to settle on fresh masks that were changed every 5 minutes.
When using jet air dryers, 89% of masks were contaminated by viruses – compared with 29% of masks when using paper towels.
Facemask contamination with virus aerosols was higher in the first 5 minutes following hand drying for both methods. Virus load was significantly higher with jet air dryer use.
In trials using jet air dryers, facemask contamination increased at 15 minutes post-hand drying, suggesting aerosolization of small particles that remain airborne for longer.
The findings will have important implications for those responsible for equipping public washrooms. Whether restaurant and bar owners or procurement managers responsible for facilities in large sporting and shopping complexes, they are likely to review the hand drying equipment that they offer. It is clear that the method of hand drying has the potential to impact airborne dissemination of microbial pathogens – including respiratory viruses – so potentially increasing risk of exposure and infection for other washroom users. Armed with this knowledge, decision makers will be eager to provide customers with the most hygienic option: paper towels.
