Performed the level 2 furnace cleaning. Burners and flame sensor are clean. Heat exchanger looks good. Combustion readings were normal. No CO detected in the air. Drain is clear. Heat rise was 51°. High limit passed the safety check. Unit is heating properly. Customers purchased an electrostatic filter. I took measurements for the size. We will need to order the filter and come back to install when we get it. We will follow up to schedule.