Smaller fan will require much more RPM for the same airflow and pressure and this will cause more (and more annoying) noise. What you want is a fan that is des

Smaller fan will require much more RPM for the same airflow and pressure and this will cause more (and more annoying) noise. What you want is a fan that is designed for particular circumstance. https://images.app.goo.gl/ULuRqRvEA6m3qYnQ8 https://images.app.goo.gl/ULuRqRvEA6m3qYnQ8 Since HEPA filter is significant obstruction you want a fan that is designed for static pressure (which is ability to push air against a force/obstruction).