Prior to every heating session, most heating contractors and furnace manufacturers will suggest having your furnace serviced by a certified heating, ventilation, and air conditioning (HVAC) supply technician. A licensed HVAC supply technician will have the proper check instruments and familiarity to check furnace issues that you as a homeowner may not know. If you have the funds to employ a certified HVAC technician, I assent that this should be done. More information: social issues