Wear face mask to prevent respiratory transmission from person to person.
Anyone using these devices should recognize that ultrasonic cleaners can be a source of airborne microorganisms ... the potential hazard ... has not been adequately assessed ... the primary source of contamination of counter tops was [is] apparently spillage and dripping  from the instrument basked not aerosolization

The microbial contamination of the counter top around the ultrasonic cleaner was not significantly affected either by the aerosol generated. If the aerosol particles were very small, these bacteria would become part of the room air flora.

Ultrasonic cleaners can be safely used and airborne contamination from this source minimized by daily cleaning of the solution tank, adding a germicide to the cleaning solution. and placing a cover over the tank while cleaning is in progress. Not assured at this time.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC275061/?page=4

Also see Block, Sterilization, Disinfection and Preservation. Chapter 30 p 676- 4th Edition