Performed preventative maintenance for gas furnace. Cleaned the burners, flame sensor and burner box. Made sure inducer port is clear. Inspected all the electrical components. Inspected the gas piping going into the furnace. Performs a combustion analysis on the furnace. System is operating at 84% efficiency with a CO level of 22ppm. Tested the amp draw of the blower and inducer. Both were operating within the manufacturer spec. System is operating properly at this time.