Complete 2 furnace heating maintenance in Lawrenceville. Change 2 16x25x1 filter. Check operations and safety. Find both 26 year old Lennox furnace operating in poor conditions and overheating and intermittent shut off on high limits. Find both upstairs blower motor worn and leaking oil. Fin s blower wheel very dirty and blower motor not running at full speed. Find flame sensor weak, find air pressure sensor worn and not pulling in properly. Inducer assembly worn and furnace chamber rusting. Both furnace also operating with high CO level and not safe to operate per NCI Safety guide line. Downstairs flue pipe PVC, not code and need to be double wall flue pipe. Due to system conditions, furnace need to replace replace and not repair.