CAN Filter CFM Ratings?

I am a little confused about the ratings listed for carbon filters on websites. My CAN filter has something called a "Maximum Exhaust CFM" which is 200cfm, and something called a "Max Recirculating/Scrubbing CFM" which is 400cfm. I have a 6" Inline Fan hooked up to a speed controller that's rated at 400cfm. I want to be clear on what these terms mean before going into flowering.

I am using a passive air intake system btw (inline fan sucking air out of a 4x4x8 room)

It means if you're running the filter at the head end of a fan/duct system that's also cooling your lights, 200 cfm is the most fan you should use.
If you're using the filter with just a fan doing no other duty, 400 cfm of fan can be accommodated. cn

I am also going to be cooling a 400w HPS in a cooltube. Will I be okay running the 6" inline fan at half speed with the speed controller? Is "medium" on the dial roughly 200cfm? Also, do a couple right angle bends in the 6" ducting reduce the CFM rating? Anyone else using a CAN33 with a powerful 6" Inline fan? Thanks!

toker89 said:

I am a little confused about the ratings listed for carbon filters on websites. My CAN filter has something called a "Maximum Exhaust CFM" which is 200cfm, and something called a "Max Recirculating/Scrubbing CFM" which is 400cfm. I have a 6" Inline Fan hooked up to a speed controller that's rated at 400cfm. I want to be clear on what these terms mean before going into flowering.

I am using a passive air intake system btw (inline fan sucking air out of a 4x4x8 room)

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"Maximum Exhaust CFM" is when you use it as a single pass exhaust any thing over 200cfm and there might be odor escaping out the end of exhaust!!
Max Recirculating/Scrubbing CFM" Means the air is not exhausted out of the room it keeps recirculating it through the filter thats why its got a higher cfm rating,Since the air doesnt leave the room it dont have to get all the smell out through the first pass!

toker89 said:

I am also going to be cooling a 400w HPS in a cooltube. Will I be okay running the 6" inline fan at half speed with the speed controller? Is "medium" on the dial roughly 200cfm? Also, do a couple right angle bends in the 6" ducting reduce the CFM rating? Anyone else using a CAN33 with a powerful 6" Inline fan? Thanks!

Click to expand...

I bought a Phresh 6x24 with a 550cfm rating to go with my 6" MaxFan which is good for 300ish. I'm using the light hood between filter and fan in a very traditional layout. I am frankly "overfiltered", but hey, on sale it was cheaper than the smaller size!
My opinion here is a bit unorthodox, but i have successfully cooled 2x600 HPS with a four-inch fan rated at a lousy 100cfm. So I think a 200cfm fan (MaxFan on its first of three settings, for example) will be entirely adequate unless you have heroic heat issues. My opinion. cn

<add> Yes, a couple of 90º angle bends with a tight radius will cost you some airflow. Imo you have room in your setup for play andor "overhead".