Chimney?

I have a fireplace that I don't use, maybe I could exhaust the flowering room through the chimney? Pack some activated carbon and we're done?

would it be noticed if there was no filter?

Yes, I would def. vent all that you can into your chimney. This is what I do and Ill list the following reasons why its smart too do the same. 1)All heat moisture, smell etc.. is vented out high enough (or at least my chimney comes out pretty high around 40' above ground) that the smell doesnt blow in your next door neighbors open windows it goes out high and stays high and floats away. Since ive vented to my chimney Ive not once smelled my room and its strong. 2) A friend of mine thats certified to run FLIR Equiment for the military explained to me, that if the cops were to come around / fly around with there FLIR equip the best spot to vent would be the chimney and not the attic or wall etc. By venting to chimey from above or side it looks like normal heat exhaust that could come out of anybodys chimney fireplace,dryer,waterheater, etc... If you vent to the attic / wall your not only putting smelly air up there, but most likely theres a pile of moisture going there also and that will destroy your walls & ceilings and cause mold on everything. Also to get back to the FLIR reasoning for not venting to the attic: you dont want one roof showing up 30-40 deg. warmer then the next one or a lower roof, thats a give away. Same with the walls you dont want one wall showing up 85deg when the rest of your walls are showing up 50deg. This is just what ive learned and done but yes I advise everyone to vent to their chimneys.