Drain odours inside can show a dry trap, broken vent

https://canvas.pasadena.edu/eportfolios/4924~6653/home/common-plumbing-leaks-that-you-may-experience-in-your-home

Sewer odours inside can show a completely dry trap, broken vent, or partial blockage; Geelong buildings with big trees or older drain lines may need CCTV inspections to locate intrusions and avoid reoccuring scents.