I have lived in my 90 year old house for 34 years. In the past two years, I’ve noticed a sewer gas smell only in the “coal cellar” and only when the outside temperature is under 15 degrees for more than a few days. My last clean-out drain, which is totally sealed, is in this coal cellar. A stink pipe is located just outside this room and comes out from under the concrete front porch steps (which were replaced two years ago). That vent seems to be working fine.
Are there any ideas or suggestions? Is this safe if I keep a window partially open? I never notice a smell in the main cellar.