Arrived to furnace maintenance. Upon arrival I made my way to the indoor units and began my maintenance. On the main floor unit the flame sensor (cleaned), ignitor, inducer motor, and blower all performed within spec. I performed a combustion analysis with this performing properly as well. The humidifier pad had calcium build up throughout and with the customers approval I performed a humidifier tune up. The air filter on this unit is due replacement and the customer will do this her self. On the basement unit the same tests/cleanings were performed with everything performing within spec. I replaced the 1” air filter with truck stock. HVAC running upon departure.