Preventative maintenance inspection/tune up on a Trane high efficiency gas furnace. Combustion analysis CO 9 PPM, O2 9.7%. Replaced a 16x25x1 filter with a company supplied filter. Verified amperage and voltage readings. Burners are slightly rusted, flame sensor was rusted and worn. Replaced flame sensor on site to avoid nuisance no heat issues based on age/condition of part. Verified proper drainage for exhaust condensation. Overall, system in fair condition for a 12 year old system. Average life expectancy is about 15 years. System is currently operating properly at this time. Trane M#TUH2C100A9V4VAB, S#10044PTC7G. Filter-16x25x1. ***Optional quote provided to replace an existing bypass humidifier with a new Aprilaire 600 series humidifier. Includes new humidistat.*** Existing humidifier has not been in use and is not recommended to use at this time.