Honeywell PRO TH4110B Owner's Manual page 10

Operating Manual
E
Set the FARswitch to Auto or On.
Set FAN switch to choose whether the fan
runs continuously or only as needed.
In '%uto" mode (the most commonly
used setting), the fan runs only
when the heating or cooling system
is on.
If set to "On," the fan runs
continuously: Use this setting for
improved air circulation, or [br
more efficient air cleaning.