Completed annual clean and service of one gas fired furnace. Removed and cleaned flame sensor. Examined heat exchanger for any signs of wear and tear and or cracks. Tested all safety switches to ensure proper operation. Replaced one 24x24x1 air filter. Took temp rise. Ensured thermostat was operating correctly. Checked gas pressure. Recommend duct cleaning. No further issues to report at this time of service. Spoke with son upon arrival and he states there is no issues with heating system he just wanted to make sure everything was up to par.