Odors travel on the wind and can be drawn into your coach just following the "breeze" down through an open vent. We had this problem, i think many do. I did install a similar device on both the black and grey tank vents. Yes a little modification to the roof to get them to fit properly, but it was not a big problem and that is why they make caulking.
Mine look like Darth Vaders hat but they are low profile white, metal, and powder coated. i got them at an RV show. the bottom line is they work, turn into the prevailing wind and draw the odor off and disperse them. Had them four years.
I do all my own stunts
03 Dolphin LX 6355, Workhorse W22, 8.1 vortec, 04 CR-V, Blue Ox, Brake Pro----Norm, Barb and
Doc(He's a PhD)