displacement slow speed fans are used quite extensively in the
tropics where the humidity is high and moisture quite plentiful
particularly on the surface of the skin.
movement of any breeze would cool the capillaries if the skin
and make conditions more bearable during the wet season in particular.
sweep fans employed in the tropics were placed someway down
from the high ceiling and avoided drawing the warm air uppermost
to the region below.
Today's' overhead fans are some thing quite different in that
their location is quite close to the ceiling, drawing the warmer
volume into play and their displacement capacity being quite
low at slow speed has a detrimental effect on an individuals
skin when exposed for prolonged periods of time at the higher
the capillaries secrete token moisture imparting a cooling effect
however when the skin is no longer able to surrender any more
moisture the skin becomes dry and dehydrates.
This is evident particularly if left on when sleeping, children
are thirsty midway through their sleep cycle and women complain
of dry skin on their faces and arms.
sweep fans need to be used prudently as they do not improve
the quality of the air as does ventilation.
ventilation is perceived as air movement whereas it is in fact
air replacement through movement
as an alternative to ventilation is based on poor assessment
and again an attempt to use one medium as a replacement for
The reverse motion used to reintegrate warm air with cooler
during the winter months has the same effect except the dehydration
occurs at a faster rate.
function is suited more to outdoor use rather than indoor as
natural currents that arise from moment to moment assist in
the ventilation through displacement.
momentum of air movement in the tropics is from side to side
and not top to bottom which is why oscillating fans located
to one side of a room are far more beneficial, although the
dehydration factor is still present