Dirty air from the dust source enters the A.C.T. dust collector at the top of the main housing. There are inlets on the roof and optional inlets on the front for the most efficient connection. As air enters the dust collector, dust accumulates on the outside of the filters as air is drawn through the high-efficiency media. The air flowing down through the system greatly assists the fallout of dust into the hopper where it is discharged. When the pulse clean system activates and accumulated dust is released from the cartridges, the air flowing downward through the collector assists dust fallout again. This avoids dust from getting re-entrained and accumulating on the filter again. Systems with vertical filters — with air entering from the side or below — struggle to avoid dust getting picked back up in the airstream or "re-entrained."