This is due to reduced air turbulence of air entering or leaving the fan. In certain situations, specific fan characteristics are needed for specialized situations. Mixing fans are generally selected for the ability to throw air. This is accomplished by use of special shrouds and deflectors that create a jet of air which travels further than normal fan discharge. Ceiling fans are also used for mixing and are not easily rated because they are free air fans.
Most ceiling fans have small motors and are relatively efficient.
Generally, these fans are sized by calculating a required quantity of air to insure proper air quality. The fan selected then provides this amount of ventilation air either by running continuously, by running on a variable speed or by intermittent operation using a cycle timer. These fans should have the characteristic of being influenced little by changes in static pressure. In other words, air delivery at 0.04 and 0.1 inches of static pressure should be nearly equal. This is to prevent substandard ventilation during windy winter conditions.