Also it depends on "what" is smelling and what is causing the smell.
in a car, there are many "things" that cause the smell. My van had what my wife calls "Man B.O." I changed the cabin air filter with charcoal lined ones every month or 2 and it always came back, and it would all come back eventually- the filter was just...umm filtering it, not the cause of it.
The car itself was not holding the smell, we could vac and clean and treat the carpets etc. - I used ozium but once it got "in the system" is was still there and it seemed like just a mask.
So then I found
https://www.amazon.com/Lubegard-96030-Evaporator-Heater-Cleaner/dp/B0007PHD0S
This cleans your AC/s innards and the coils. If it is really really bad, get 2 and do it from the inside access and the outside access.
So I used the coil cleaner, replaced the cabin air filter and used ozium for any general cabin stuff like kids leaving random food crap in the car or carpet areas that are dirty. After doing all of this and very thorough - it was nice and kept smelling neutral.