Old fashioned oil and coal furnaces were not electric

The Dyson Air Multiplier fans, and the Imperial C2000 series range hood fans,[7] have no exposed fan blades or other visibly moving parts. The airflow is generated using the Coanda effect; a small quantity of air from a high-pressure bladed impeller fan, contained in the base rather than exposed, drives a large airmass via a low-pressure area created by the airfoil.[8][9][10] The US Patent & Trademark Office initially ruled that Dyson's patent was not an improvement on the Toshiba patent on a nearly identical bladeless desktop fan granted in 1981.[8]
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, usually generated by a fan in the base of the cabinet.
Convective[edit source | editbeta]
Differences in air temperature will affect the density of air and can be used to induce air circulation through the mere act of heating or cooling an air mass. This effect is so subtle and works at such low air pressures that it does not appear to fit the definition of a fan technology. However, prior to the development of electricity, convective airflow was the primary method of inducing airflow in living spaces.
Old fashioned oil and coal furnaces were not electric and operated simply on the principle of convection to move the warm air. Very large volume air ducts were sloped upwards away from the top of the furnace towards floor and wall registers above the furnace. Cool air was returned through similar large ducts leading to the bottom of the furnace.
Older houses from before electrification often had open duct grilles leading from the ceiling of a lower level to the floor of an upper level, to allow convective airflow to slowly rise up the building from one floor to the next.
Outhouses commonly rely on a simple enclosed air channel in a corner of the structure to exhaust offensive odors. Exposed to sunlight, the channel is warmed and a slow convective air current is vented out the top of the building, while fresh air enters the pit through the seat hole.
Electrostatic[edit source | editbeta]
An electrostatic fluid accelerator propels airflow by inducing motion in airborne charged particles. A high voltage electric field (commonly 25,000 to 50,000 volts) formed between exposed charged anode and cathode surfaces is capable of inducing airflow through a principle referred to as ionic wind. The airflow pressure is typically very low but the air volume can be large.
However, a sufficiently high voltage potential can also cause the formation of ozone and nitrogen oxides, which are reactive and irritating to mucous membranes.
Noise[edit source | editbeta]