Squirrel Cage Blower Selection (Gorgous)

We habitually here an inquiry like this one: I have a squirrel confine blower and I'd like to assemble an air channel for my shop, yet the blower doesn't have any markings so I don't know how much air it will move. How might I decide the CFM of the blower, and will the CFM influence the extent of the channel I should utilize? It would appear the more air you're moving, the more square creeps of channel you ought to have, or does it truly make a difference ?