Does changing fan speed with a controller effect what size carbon filter I should get

I am looking into getting my ventilation equipment and am wondering what size carbon filter I should get. The fan/filter I want to purchase is way larger than I need for my tent but gives me upgrade options in the future. While my grow is legal, I want it to be as quiet as possible while effectively removing any smell. I figured getting a speed controller for an over size inline fan lets me turn it down quite a bit while maintaining appropriate air movement. By doing this though, lets say I was running a 650CFM fan at 50% does it basically make the fan comparable to a 325CFM? If that is the case would a 650CFM carbon filter be too big? I know that how I run my ducting will also change my overall cfm but that aside should I get a carbon filter that matches the CFM rating of the fan or what the CFM will be closer too when using the speed controller?

The cfm rating given by a carbon filter is the maximum.
You can run it lower no problem.

Do the sniff test each time you come home if you are worried.

By turning the fan down using a controller by 50% will not insure a 50% drop in air flow. In saying that if your room is for example 8x8x8 you would be changing more than half the air every minute so even if you were less than that there should be no issues. I use a hepa with a charcoal canister that is rated for 150 cfm and that is for a whole house application. I have no issues with odour but my area is completely sealed (I use CO2). Also keep in mind that in order to keep noise to a minimum regarding air noise (under 700fpm) you would need around 250 sq inches of intake duct if not passive.

Do the sniff test each time you come home if you are worried.

Click to expand...

Thats what I do lol