I usually dont say much but this is something that i want to chime in on. I have been pushing through a filter rather than sucking through for years. Actually i have never pulled through the filter. With that said, my filters have always been a higher CFM than my fan to avoid the burn out theory. 500 cfm is 500 cfm in or out, the concept is ideally the same. You are either pushing or pulling particles through a bed of activated carbon. Not trying to start a debate, just putting out my experience with them and the life of my fan has been great.