No. Assuming you have one HVAC unit (heater/air conditioning unit) for your house, you would just place MarCELL in one of the rooms serviced by this HVAC unit. If this room is within cellular range, then you know your HVAC system is working. If you have a large house, multi-tenant dwelling or large commercial building serviced by multiple HVAC units, you would want to place one MarCELL in every zone.