Yeah man, these guys have pretty much summed it up tanman. 100% odour controll comes along with a price unforutnately.
Carbon filter is the way to go. And some good info from dankshasta there, i fell for the 'too small a filter for the job one'. If you can go with a carbon filter, get a rhino !!!
Like nickyp, i also have a carbon filter that is more than adequte for my space and has larger cfm than my extraction fan. I get zero smell.
But the thing is the fan, you need a fan for a filter and the fan is noisy, so whereas your dealing with the smell issue your also bringing in another noise issue.
So i think that just leaves you with trying to make some sort of diy scrubber or sumthin with a few pc fans depending on how big yor closet is.
I stupidly bought a can filter 1500 which was only rated at 75cfm. {i didnt realise there was a big difference in filter cfms etc} Anyway, its rated at 75cfm and then just use a pc fan rated around that mark and extract with that? Maybe sucking from and blowing out into the filter rather than sucking through it as they are most commonly used.
Im def no expert btw and not sure if it would work, and im still on my first grow, but i was thinking of maybe trying it out for a drybox.
Have you looked into a pc case grow of some sort and a small diy scrubber ?
https://www.rollitup.org/cfl-growing/311365-first-grow-scrog-pc-case.html
Not get much bud, but its a start.
Ona aint too bad too to an extent, but i think its ok for backup if your setup isnt 100% but i dont think it can be used in place of another odour control device. You would need a shitload of it and questions would still be being asked as to wtf that smell is.
Im sure it can be done mate. But i wouldnt like to try grow without a carbon filter. And i wouldnt underestimate the smell of even just two 'low odour strain' plants in flower.
Just my 2p. Good luck.