text: Dyson Air Multiplier fans introduced to the consumer market in 2009 have popularized a 1981 design by Toshiba that produces a fan that has no exposed fan blades or other visibly moving parts (unless augmented by other features such as for oscillation and directional adjustment). A relatively small quantity of air from a high-pressure-bladed impeller fan, which is contained inside the base rather than exposed, induces the slower flow of a larger airmass through a circular or oval-shaped opening via a low-pressure area created by an airfoil surface shape (the Coandă effect).
  Air curtains and air doors also utilize this effect to help retain warm or cool air within an otherwise exposed area that lacks a cover or door. Air curtains are commonly used on open-face dairy, freezer, and vegetable displays to help retain chilled air within the cabinet using a laminar airflow circulated across the display opening. The airflow is typically generated by a mechanical fan of any type described in this article hidden in the base of the display cabinet. HVAC linear slot diffusers also utilize this effect to increase airflow evenly in rooms compared to registers while reducing the energy used by the air handling unit blower.