[amluto]

The pressure drop across a HEPA filter is a function of flow rate per unit area (i.e. velocity), and it can be very very low if the velocity is low. You only need some 15 cfm per person, which isn't very much. The real issue that that a HEPA filter that will achieve extremely low pressure drop is rather bulky.

[bizzz]

Thank you both! I'll start with a small research into available HEPA filter sizes, pressure drops they entail, and noise vs power ratio of available fans. Then I'll see if any combination fits my trickle vent setup and theoretically gives enough air as an output.