Furnace maintenance in Duluth, Georgia. Two systems. Changed filters. Tested mechanical and electrical components. Found upstairs system with worn flame safety sensor. Recommend repair. Neither system has an overflow protection switch as a secondary form of water safety, recommend adding on to serve as a backup to primary water safety and to help protect furnaces from potential water damage. Upstairs gas line is not up to code as it has no drip leg, recommend installing drip leg to bring furnace up to code. Systems are heating at this time.