> This isn't in the building, it's The building drainage system in many areas is not "protected" by a house trap. Many municipalities require a backwater water

> This isn't in the building, it's The building drainage system in many areas is not "protected" by a house trap. Many municipalities require a backwater water valve which is essentially a check valve with a mechanical moving part. I can easily envision (and I have held a Master Plumbers License) this failing. Furthermore once you trench to bring sewer, and water into a building (these services while in a manner of speaking are kept separate they often share a common or very nearby trench) it's very easy to not backfill properly thereby also allowing vapors to enter a structure in some instances. It depends: did they use dynamite to blast for the foundation or to bring in these services? There are all kinds of variables that could allow trench to building fumes. I agree people do freak involving odors, but on the other hand different people have different actual physical tolorances to chemicals.