Preformed maintenance on 2 Goodman furnaces from 2005. Checked safeties and pressure switches, cleared drain on condensing gas furnace in crawl space, cleaned flame rod. Checked duct work it’s R-6 and it’s sealed. Home owner mentioned that when the first floor comes on he starts to sneeze checked duct work for tips or holes in it also checked plenums it all was good, told him if it really becomes a issue to call Mad Hatter to get ducts cleaned.