Not necessarily. Obviously the one where you attach the fan is closed off. For the other two, if I'm smoking at 275F or less, I keep them all closed. If I'm zooming along at 300F+, which I often do with poultry in the 325-350F range, or if I'm in just in a hurry with a butt or some other cut of meat, I'll open them all the way to maximize air flow and coal stoking.
Thanks for the reply. Question all the bottom vents have to be closed right?
Dan