Performed furnace and tankless water heater maintenance. 16-year-old Lennox furnace is still operating normally. No signs of water damage, and internal components appear clean. Cleaned flame sensor and condensate tubing. Checked heat rise and performed combustion analysis—furnace is operating within normal parameters. Flushed tankless water heater for 45 minutes with a descaling solution. Cleaned condensate trap and air intake, and inspected all components—tankless water heater is in good condition. Both appliances are operating within manufacturer specifications.