Just from a practical standpoint, unless the exhaust fan is located on
an exterior wall, it is easier to vent the fan if it is in the
ceiling. Mounting the fan in an interior wall presents the problem of
running the duct, presumably 3"-6", through the top plate of the
wall. A ceiling mount allows you to duct to the outside via attic, or
the space between joists.

On May 30, 9:11*am, "Bill" wrote:
Why are bathroom exhaust fans mounted in the ceiling?

Wouldn't down low next to the toilet be a better location?

Maybe even lower than the toilet and behind the toilet. Then the "smell"
would go down and back instead of forward and up!