Arrived to do a performance maintenance. 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 for the system is collecting dust. Checked systems heat exchanger to ensure proper venting of flue gas. Found bacterial growth present on the bottom of the evaporator pan. Verified operation of the humidifier. Found that the humidifier panel is coated in calcium buildup and bacterial growth. While packing up tools the pvc vent dripped next to me. Found that the furnace exhaust is leaking flue condensation. Spoke with homeowner about the system. Furnace and humidifier are operational at this time.