High-volume low-speed fan

In the late 1990s, William Fairbank, a professor at the University of California at Riverside, and Walter K. Boyd, founder of MacroAir Technologies, invented and patented a new type of circulator fan, first called a High-Volume, Large-Diameter (HVLD) fan.

Once the floor jet reaches its potential, it migrates outward until it meets a side wall or other vertical surface.

[8] Under ideal conditions, an 8-foot-diameter (2.4 m) fan produces a floor jet of air approximately 36 inches (910 mm) deep.

While some fans use contemporary blades to move air, other methods are being used to make it more efficient such as using airfoils.

While the cross-sectional area varies with the square of the diameter, the large column has proportionately fewer peripheries, and therefore less drag.

In general, Air Movement and Control Association Standard 230 sets uniform testing procedures for determining ceiling fan performance.

AMCA 230 establishes uniform methods of laboratory testing for air circulating fans in order to determine performance in terms of thrust for rating, certification or guarantee purposes.

The current version, AMCA 230–12, reintroduced airflow rate with a revised equation, and new efficiency metrics.

In still air, layers of constant temperature form, the coldest at the bottom and the warmest at the top.

To avoid causing a draft, fans need to be run slowly so that air speed at the occupant level does not exceed 40 feet per minute (12 m/min).