6 inch ducting ok for a 4 inch carbon filter?

LWD

Active Member
Hey RIU, well here goes this story bear with. I bought a 4 inch carbon filter along with a 4 inch fan. However the light I want is a 6 inch air cooled hood, and I already bought the 6 inch inline fan for it. Do I have to buy another 6 inch carbon filter, or can I rig 6 inch ducting to a 4 inch carbon filter? Is there any sound way to do that?
 
It all depends on the cfm of filter.. If air is moved too fast thru it then it doesn't have time to scrub air clean.
 
I do this exact same thing... 4 inch carbon filter, rated at 200 CFM with a 6" to 4" reducer attached to 6 inch ducting and I use an exhaust blower rated at 180 CFM... Its the CFM ratings that you should go by in trying to figure out if your air-moving equipment is compatible with each other... You want the fan/exhaust CFM to be lower than the CFM rating on your carbon filter.
 
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