[asynchronous13]

> Gasses and odors of any type shouldn’t be able to work their way back into a building via the sewer pipes.

I don't see any claims in the article that the odors entered the building via the sewer pipes. What makes you think that was the path that the odors followed? It could have just as easily been through an open window, or the pipe work could have been near an HVAC intake for the building.

[dillonmckay]

HVAC intake?

I don’t think new air would be introduced unless the system contains an HRV or ERV.

Additionally, this sounds like improper venting, which is a surprisingly common occurrence.

So the gases could be coming up from the drains and toilets.