Question: I have recently begun to check into gas logs for an existing masonry fireplace- and as I do not have natural gas- propane is my answer of choice.I want them to take the chill off an occupied family room (not sleeping quarters) of approximately 300 sq ft.I have tried the local distributors- and have received as many opinions as dealers. Some say unvented- some vented- some say "no problems- best thing since sliced bread...". Some say "...but they never tell you the down side!"The other- and I think- most troublesome issue is condensation. I am being told by one local distributor that the unvented models will deposit as much as 1 gals per hour of condensate water into my attic. Expect ruined insulation- wallboard- etc..I think I prefer the partially vented models anyway- simply because my wife is particularly sensitive to the smell. However- some vendors tell me that I CANNOT vent the unvented models. If you are sensitive- then you may want to stay away from unvented The Vent-Free CAN be used with the damper opened or closed. Answer: Unvented are the only thing that will produce HEAT- vented are just for looks....Another option- which costs more $$ but solves all the problems- are vented gas inserts...sealed and vented and lots of HEAT. As far as condensation- if you are going to use vent-free 1-4 hours per day- there should be no problem. If your wife or anyone in the family is very sensitive to odors, I would suggest looking into an insert or other vented appliance.