Inspected furnace for cause of overheating and found no major concerns with unit gas pressure at 3.10 blower speeds on high. Filter was clogged with white dust suspected from humidifiers. Advised to run purified water or replace humidifiers with a whole house installed in the hvac. Found loose exhaust clamp for furnace. Tightened clamp down and informed homeowner of concern. Advised maintenance should be performed 2 times a year once spring once fall.