Sewer odours inside can show a completely dry trap, fractured vent

http://photohistory.oregonstate.edu/works/half/the-importance-of-regular-plumbing-maintenance

Sewage system odours inside can show a dry trap, split vent, or partial blockage; Geelong homes with large trees or older sewage system lines may require CCTV assessments to find invasions and stop reoccuring scents.