Instruct: Classify an Amazon review as either positive or negative.
Query: HVAC in line booster fan.

Almost Noiseless and is vibration free. HAD to install this on a rotatable bend in the ductwork that came off a rectanular feeder which attached immediately to an enclosed 6" round. The attachment panel trimmed easily and the motor bracket even had addtitional holes to center the fan for blade clearance. Even on the bend it pumps out prodigous amounts or air at the flush mount floor grill. I now have two of these in parallel on a variable speed control adding much needed boost to an A\V equipment room. At full speed it can be distracting but I run both fans at 3/4s and hardly notice them in an otherwise silent room. With the A\V gear in full operation, even run together the fans are unobtrusive and forgotten. You could wire them into your HVAC system I but then they would only run when the HVAC system comes on and would operate at full speed.