Arrived for furnace maintenance today. Checked static pressure and found it is failing at this time. Ran combustion analysis to make sure fuel is burning properly. Checked temperature split between the return and the supply air. Checked heat exchanger and found rust in several spots. I contacted my field supervisor Dre, and he came out to recheck my findings. Rick wanted to with Dre about replacement options. System is running upon departure. Thanks for choosing LBA.