AMDMB has upped a guide on general fan performance. Snip: CFM is an often-confusing term because it has no single definition that applies to all instances. In the most basic sense, CFM means cubic feet per minute. Sounds simple enough, doesn?t it? Unfortunately, air is a compressible gas. This means that if you put one cubic foot of air into a balloon at sea level and then go climb a mountain, you?ll have more than one cubic foot of air atop the mountain. Sound confusing yet? For the full guide use warp: Engage!