There was a secret open drain to nothing inside the wall behind the furnace, branching off from the sewer line coming down from the kitchen, venting up rotten gasses from the depths of hell right into the air return path.
No idea what could have been down in the furnace room once up on a time to make use of that drain. Not sure why it was just walled off instead of closed when the furnace was installed in front of it. Hard to say why it would have taken this long for the trap to dry up. But shame and frowns and shaken fists upon whoever decided that HIDING AN OPEN SEWER LINE INSIDE A WALL USED AS AN AIR INTAKE WAS A REMOTELY O.K. THING TO DO.
Anyway, after ripping open the wall, capping off that pipe, and venting out the house once more, I can sleep in a room that is both cooler than 88° and does not smell of death, which, let me tell you, is pretty swell.
A week and a half later, I still can’t use the air conditioning, and the rotten stench is getting steadily worse. I paid an HVAC guy just to come out, look around, and shrug. A plumber-and-everything-else friend of mine came over to investigate, but couldn’t find anything going on with the plumbing, or any methane leaks anywhere.
The smell started only a couple weeks after I stopped using the basement shower, so I though maybe there was some dried-up trap down there letting sewer gasses through, but I ran the water down there again to no avail. My friend even found a dead mouse on top of the ducting in the furnace room that looked like it’d died a little over a week prior. Perfect timing and location – surely that must be it. No. Got rid of that and aired out the furnace room, but the smell is still coming, stronger than ever.
Maybe there are other dead mice in the ducts themselves that conveniently died at the same time as the other. Maybe I’ve been infested by a mouse suicide cult on a mission to make everyone have a bad time. Maybe it’s still something completely different and there are simply a number of wild coincidences strewn about to throw me off.
I’m at my wits’ end. Getting desperate. This is not O.K.