I sometimes had a sewage smell coming out of my vents on the second floor. I called Legacy Air based on all the great reviews. The tech was scheduled to come out between 3pm and 7pm. Greg the technician called at before 2pm and said he could come out sooner. Wow! I was impressed usually a/c companies never come on time. Greg did a thorough inspection of the units, the furnace, the pipes etc. He found nothing wrong with anything. He explained to me whatever was causing the smell when the a/c is turned on it will pick up the odor and disperse it throughout the room and hallway. I have to admit last night and today I smelled nothing coming out of the upstairs vent. Well next call will be to the plumber. I paid him for the visit and will call continue to call Legacy for my a/c. It is true they are not going to sell you something you don't need.