How do I match a filter to my fan?

So I understand that I need to match my fan cfm to my carbon filter, and if I was just placing the fan on top of the filter then this would be a very straight-forward task....

But what if my fan and filter are on opposite ends of a network of ducting and lights?

Do I match the filter to the advertised cfm of the fan? Or do I match it to the cfm of the fan minus all the negative effects of ducting and 90 degree bends, etc?

tillygrower said:

So I understand that I need to match my fan cfm to my carbon filter

Click to expand...

Not really. Filters are rated at maximum cfm. The bigger the filter the less the resistance. I always oversize carbon filters.

Obviously fans lose cfm to resistance. This rate is not linear. Axial and hybrid axial lose more than centrifugal. The better manufacturers post x-y charts with rated cfm when using different carbon filters or at least different pressures.

This will give you a good idea of what you should get.

- Jiji