J.H.
My wood floor was ruined by a cool mist vaporizer. I don't know if it was not working properly but the mist traveled down the side, down the storage bin it was sitting on, and onto the floor where it ate away the finish in one night.
I've had great luck with the Vicks warm mist vaporizer. As with any vaporizer you do need to clean it regularly to keep it from getting cruddy but most of the parts are dishwasher safe.