I recently purchased a house in New Jersey which was build in 1926. I had it inspected and there were no major issues. It is balloon frame construction and has blown in wall insulation. There is a house fan in the finished attic which will move quite a bit of air and create a nice circulation when the windows are open downstairs. I noticed a strange smell in the house which I thought was coming from the upstairs bathroom, upon further investinagation I found that in a closet that shares the wet wall with the shower, there is a large hole cut in the back and in the floor to access the tub/shower plumbing (We did not catch this on the inspection) and when I run the house fan it sucks air out of this space. I wouldn't classify the smell as sewage, but it is less than awesome, maybe like the sink drain when you have the pipes open and a combination of dog and wet cardboard. I do have an unfinished and is a bit musty, I have a dehimidifier on the way, and it has been very hot an humid for the last month. So the obvious answer is to repair the floor and wall and seal it up. The question I pose, is this smell normal for the inside of the walls of an 80 year old house or does it warrant further investigation.