Performed preventative maintenance on Lennox furnace model #g60uh-60c-110-03, serial #5802L 18384. Upon Arrival the system was calling for heat. I took a combustion analysis test and received the following results, o2 is 12.2% and the co levels are 8ppm. The inducer motor amp draw is .4. I powered the system down and removed the access panels. Removed and cleaned carbon off of the flame sensor and cleaned out the burners and burner box. Checked the pressure switch for clogs and tested the drain line and condensate pump with several bottles of water to ensure that there are no Leaks or clogs. Performed humidifier service for a aprilaire 700 series. Removed and replaced the old water panel. Cleaned out the housing and drain. Replaced the pure air kit supplied by the homeowner. Powered the system back up and tested the system for proper operation.the system is operating properly at this time.