But in bathrooms where such plumes gush regularly, where does all that fecal bacteria go?
In theory, adding high-efficiency particulate air (HEPA) filters should stop bacteria particles from spraying over your newly cleaned hands. That's the word, but a new study by University of CT scientists finds they spread fecal matter onto people's hands, CNET reports.
Hot-air hand dryers in multiple men's and women's bathrooms in three basic science research areas in an academic health center were screened for their deposition on plates of (i) total bacteria, some of which were identified, and (ii) a kanamycin-resistant Bacillus subtilis strain, PS533, spores of which are produced in large amounts in one basic science research laboratory.
"Bacteria in bathrooms will come from feces, which can be aerosolized a bit when toilets, especially lidless toilets, are flushed", study author Peter Setlow told Newsweek. The results were published recently in the journal Applied and Environmental Microbiology.
A plate sample of typical bathroom air sampled an average of less than one colony; however, a plate held underneath a hand dryer for 30 seconds had 18-60 colonies. The bathroom air samples returned substantially fewer colonies than the hand dryer sample. So, in the brief moments your hands rest below the nozzle, they'll be exposed to far more air than usual-and far more bacteria. Dryers could act as "reservoir" for bacteria, they suggested, or perhaps their intense blowing simply provides more exposure to the already contaminated air. The team was actually seeking a benign lab-engineered bacteria, which they found in each bathroom, showing how easily it had spread through the whole building, notes Yahoo.
For now, Setlow is sticking to paper towels-as is the University of CT, which has added them to all 36 bathrooms surveyed in the study.