Well everyone's needs are different... I grow one plant at a time in a 2x2 tent in my basement. I finally broke down and bought a ventilation fan & carbon filter, one of those Amazon specials lol.
I'm in a townhouse complex and even though it's legal (
) I don't want to 'advertise' that I'm growing and more importantly the wife doesn't care for the smell of the fragrant flowers I grow
For you it's going to depend on the size of your tent and closet. You'll need to figure out the CFM (cubic feet per minute) for your size tent and base your fan/filter needs on that number.
But yeah you'll need some serious filtration in order to keep odors in check...especially if you've got neighbors in close proximity!✌