TRUTH: It is recent trial to increase exhaust velocity by adding an additional blower fan at the exhaust side improving air circulation in the room and expecting particles be pushed into the device.
Theoretically, most air purifiers are designed to use expelled exhaust to push clean filtered air around the room, creating enough velocity to push particles back to the intake of air purifiers. This may work impressively in a controlled test chamber but in the real world of larger room sizes, the power of this exhaust is sorely insufficient. In addition, room furnishings and fixtures create obstacle courses that disrupt ideal flow patterns.
Moreover, when a door opens, it will push air out further decreasing the force that may be able to feed particles back into the device. These effects are not factored into testing chambers, skewing results and prompting specious conclusions.
Direct capture and removal of all harmful particles is simply not possible for any fan-driven devices.