How can you automate fans to reduce moisture/mold?

[Scott Price]

We have a recurring issue with mold appearing in various places in various units.  Proper ventilation would likely eliminate it, though the tenants do not make the effort to use or leave on ventilation fans.  I was wondering what automated solutions you may have used successfully?  I have been thinking about whether or not a low volume / quiet/ always-on bathroom fan with a selectable high volume mode connected to the wall switch may exist.  We have also used automatic humidity sensing switches, though the results are sporadic plus it does not allow for the fans to be run during low humidity scenarios when a fan is still desired (they should be enable to run the fan as much as possible).  Any ideas?