Performed preventative maintenance on a gas furnace. Inspected all the electrical components. Confirmed proper high and low voltages . Replaced the customer supplied #501 air filter. Cleaned the burners, flame sensor and burner compartment. Performed a combustion analysis on the system. System is operating at 81% efficiency with a CO level of 25ppm. Set the new power humidifier to preferred humidity of 35%. The humidifier #35 panel will need to be replaced next season since it was installed at the end of the heat season last year. System is operating properly at this time. Model #G60UHV-60C-110-07 Serial #5907K03650