Harold pretty much sums it up. Respiratory and moisture problems usually 'show up' after a while depending on use. At the same time, setting all that aside, I'm of the unsolicited opinion that vented ANYTHING is the way to go. It just doesn't seem healty otherwise.
My best to ya and hope this helps.
Jay J -Moderator
See Venting for more info. A vented unit is about 70% efficient vs. 100% unvented. If you have condensation on windows now, it will get worst for sure.