I performed a 2 system heating maintenance on 2019 gas systems. I checked amps, capacitors, filters, electrical, drains, cleanliness, ducts, insulation, safeties, and provided a visual inspection of the outdoor units. I noticed that the ducts are beginning to build up dust again. I provided options to address these area of concerns. I offered upgrading the filters, duct cleaning, and air scrubbers. Customer did not approve estimates at this time.