Performed Furnace Maintenance: Downstairs - Checked filter - Wiped down furnace - Cleared debris - Checked for carbon monoxide - Cleared pressure switch hose - Checked gas valve - Checked temperature at supply - Checked temperature at return - Checked supply grills for airflow - Cleaned and polished flame sensor - Checked igniter - Checked control board - Tested inducer motor - Inducer motor registering at 2.0amps - Tested blower motor - Performed static test on system - Return side measuring at .4WC - Supply side measuring at .2WC - Checked supply side air temperature:118 Degrees - Checked return side air temperature:78 Degrees - Temperature Split:40 Degrees - Performed Combustion check on system - System measuring at 22PPM carbon monoxide - System measuring at 11.1% oxygen Average lifespan for an Furnace is 15-20 years. This current Furnace is 21 years old which puts it over its lifespan and in prime position for major component failure to occur. Suggest replacing Furnace Indu