Changes

In addition to all of the aforementioned factors, there are certain other factors which have an effect on a fan's '''''perceived'' efficacy''' (how efficacious an observer experiences a fan as being):

In addition to all of the aforementioned factors, there are certain other factors which have an effect on a fan's '''''perceived'' efficacy''' (how efficacious an observer experiences a fan as being):

* ''Height of the fan relative to the observer''. The closer the fan is to the observer, the more air movement the observer will feel. A fan mounted close to the ceiling in a high-ceilinged room will have a lower perceived efficacy than if it were mounted closer to the ground.

* ''Height of the fan relative to the observer''. The closer the fan is to the observer, the more air movement the observer will feel. A fan mounted close to the ceiling in a high-ceilinged room will have a lower perceived efficacy than if it were mounted closer to the ground.

* ''Tilt of the fan's blades relative to the [[Cartesian coordinate system#In three dimensions|Z-axis]]''. A few fan manufacturers, notably FASCO, constructed their fans such that the blades had an "up-tilt"; that is, they were tilted relative to the Z-axis. While this increased the area of the room over which the fan had a direct effect, thereby increasing the efficacy perceived by persons standing at the edges of the room, it decreased the airflow concentrated immediately under the fan, thereby reducing the efficacy perceived by anyone standing/sitting directly underneath it.

* ''Tilt of the fan's blades relative to the [[Z-axis]]''. A few fan manufacturers, notably FASCO, constructed their fans such that the blades had an "up-tilt"; that is, they were tilted relative to the Z-axis. While this increased the area of the room over which the fan had a direct effect, thereby increasing the efficacy perceived by persons standing at the edges of the room, it decreased the airflow concentrated immediately under the fan, thereby reducing the efficacy perceived by anyone standing/sitting directly underneath it.

* ''Humidity of the room''. Since a fan creates its cooling effect by speeding the evaporation of moisture (both sweat and ambient humidity) on human skin, its perceived efficacy is directly correlated with the amount of [[humidity]] (moisture) in the room. In dry environments, such as desert climates, a fan has a lesser perceived efficacy than in humid environments; this is especially notable during cold weather, where a humid environment has a pronounced wind-chill effect which is lacking in dry environments.

* ''Humidity of the room''. Since a fan creates its cooling effect by speeding the evaporation of moisture (both sweat and ambient humidity) on human skin, its perceived efficacy is directly correlated with the amount of [[humidity]] (moisture) in the room. In dry environments, such as desert climates, a fan has a lesser perceived efficacy than in humid environments; this is especially notable during cold weather, where a humid environment has a pronounced wind-chill effect which is lacking in dry environments.