Do any of us really know what the CFM of these blowers is, especially after most of us have fiddled with the speed. I lowered the speed on mine for that reason and to reduce bridging. I also thought I could reduce wear and tear on the ceramics. I think I'm down to less than 50 percent right now. I suspect the flow accelerates appreciably at the nozzle during combustion and the addition of secondary air. We all know what the flame looks like on a propane torch looks like when we block off the secondary air.