Report as inappropriate

Depends on what you are trying to accomplish. Here are some thoughts:

  • Enough filtered air needs to be exhausted to provide a slightly negative enclosure internal pressure. This keeps the nano particles in the enclosure.
  • For materials such as ABS where bed temperatures are high (100 deg C) more air needs to be exhausted so that cooler outside air can be used to cool the interior of the enclosure.
  • For PLA the temperature is relative low and less cooling air is needed.

I have supplied a restrictor that will divide the air about equally between exhaust and recirculate. Since this is a simple shape you can make your own restrictor to better suit your specific needs.