Arrived onsite for heating maintenance 2 gas fired furnaces 1 in basement and 1 in the attic. Attic Furnace unit: Ask customer to turn heat on and confirmed operation.. Brushed and Wiped down furnace blower cabinet and gas burners. Burners fired and are in good working order. No visual impingement detected. Checked electrical. Cleaned the flame sensor. Measured temperature rise at 36 degrees. System is operating as it should. Basement Furnace: turn heat on and confirmed operation. Changed the polarized filter. Brushed and Wiped down furnace blower cabinet and gas burners. Burners fired and are in good working order. Blew out condensate line. No visual impingement detected. Checked electrical. Cleaned the flame sensor. Measured temperature rise at 56 degrees. System is operating as it should.