2017 Lennox high efficiency furnace running in great condition. 16x25x1 air filter in good condition. Clean flame sensor and check ignitor. Visual inspection of burners. Flush condensation trap and drain lines. Inducer and blower motors operating within spec. 2" pvc flue in good condition and no sign of leaks. 0PPM CO detected during testing in furnace area. Run test furnace in heating mode from thermostat. Delta t of 59F with supply temp of 130F, spec Delta t of 40-70F. Furnace is operating properly and ready for Winter.