Arrived to do a performance maintenance. Verified temperature split in heat pump mode. Switched over to gas heat. Set up for combustion analysis temperature split and static pressure tests. Verified operation of all mechanical and electronic components of the furnace. Checked blower for cleanliness and to see if there is any play in the bearings. Found heavy dust buildup on the blower wheel. Checked systems heat exchanger to ensure proper venting of flue gas. Found dust on the heat exchanger from the blower wheel. Verified operation of the humidifier.