Have not got the new air filtration yet, But, do have a good fan and full sized screen door for the Bilco Door. If I have all the Basement windows open , have the fan running and leave the Bilco door open ; how much air filtration am I going to get ? The screen door in the Basement that leads up to the Bilco door, is a full screen door. 36x 77. Odd size, but that is what the opening is for the door. 5 Basement slider windows.