It's meant for hands that were just washed. I understand that not everyone does a great job washing, but I have a hard time believing this poses a real threat..
> Participants washed their gloved hands with a suspension of MS2 bacteriophage and hands were dried with one of the three hand-drying devices. [...] Over a height range of 0·15–1·65 m, the JAD [jet air dryer] dispersed an average of >60 and >1300-fold more plaque-forming units (PFU) compared to the WAD [warm air dryer] and PT [paper towels] (P < 0·0001), respectively.[1]
Okay, but I'm sure just-washed hands aren't all that dirty, right?
> This observational study was conducted to evaluate [...] hand hygiene practices among college students. [...] Overall, 72.9% of students washed their hands, 58.3% practiced hand hygiene (using either soap or hand sanitizer), and 26.1% washed their hands adequately.[2]
I couldn't find any epidemiological studies, but this feels like good enough of a reason to stick to other options considering these things are a solution in search of a problem anyway.
You’re lucky if people even make a show of washing their hands. If they wash them well, then you have just met a unicorn. And even people who do normally wash their hands well sometimes run into issues like there not being any goddamn soap stocked (in the same bathroom, 3 days in a row).
Don’t use the air blowers; just let your hands air dry if there’s no paper towels. It doesn’t take very long and has been basically my standard practice for about 10 years now.