WHAT MAKES DIRT EATER UNIQUE?

Why air purifiers need to be boxy?
And continuously needs to be connected to electricity and need to be kept near a wall? Why they use small fans which make a lot of noise and limit it efficacy?

With the application of some common sense, we removed the box and fan; and put the air purifier at the centre on a larger fan you were already having

The regular Air Purifiers kept in a corner were slow and covering only a small portion of the room.

DIRT EATER IS FAST AND COVERS THE ENTIRE ROOM.

What's more, 
1. Does not take space on floor, 
2. No body can see it working
3. No electricity required
4. Works quietly