Should the HVAC appliance fan or blower run continuously?
No. This is not necessary. During normal operation of the heating or air conditioning, the blower will circulate the air over the UV bulb from 50-75 times a day, which is sufficient. During moderate weather, when neither the A/C or heat is on, it is recommended to open the windows to allow for fresh air infiltration and/or to operate the blower continuously (turn on the fan) to circulate air over the UV light.