Home, a smelling place

Isn't home such a sweet smelling place? I recently arrived home after 19 hours or so on the road, only to discover my home doesn't smell so great. It's a mixture of sulphur, decay and something undefinable. I had the gas company come out and we were all good there, except they had to install themselves on my list of "Really, don't call these people unless you are good and sure you have a gas leak". I say that because after telling me that I did not have a gas leak, he then told me that he had turned OFF my furnace AND my water heater (no I had not had the privilege of showering yet) for some various and not so very good reasons. He also said that I needed to have an HVAC guy come out and take a look at the problem. Welcome home to me! So HVAC is here and says it smells of sewer. Yum, I knew it was going to be good. So all of this to say, enjoy your sweet smelling home, I've got the smelling part cornered, just got to find the sweet.