Arrived to do a performance maintenance. Set up for combustion analysis temperature split and static pressure tests for each system individually. Verified operation of all mechanical and electronic components of each furnace. Checked blowers for cleanliness and to see if there is any play in the bearings. Found that the Goodman system is starting to collect dust and the ruud system is heavily coated in dust. Checked systems heat exchanger to ensure proper venting of flue gas. Both furnaces are operational at this time.