Arrived to do a performance maintenance. Upon arrival noticed flue condensation leaking out of the exhaust piping. 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 that the fan is coated in dust debris. Checked systems heat exchanger to ensure proper venting of flue gas. Verified operation of the humidifier. Found the humidifier panel is coated in calcium buildup. Spoke with homeowner about the system. With homeowners approval replaced the panel in the humidifier. Furnace and humidifier are operational at this time.