Free shipping and returns. The powerful VortexAir technology brings air in from 360-degrees, which is why it can purify your 403 square-foot space 5x times an hour! The Core 400S not only traps particulate matter like dust, fur, lint and hairdown to the tiniest particles, zero-point-three microns! How big is a micron? a human hair is SEVENTY microns thick! You'd need 500 times magnification to see a single micron!