Sewage system odours inside can indicate a dry catch, cracked vent

https://learn.multnomah.edu/eportfolios/918/home/why-you-need-a-plumber-to-clear-blocked-drains

Sewer odours inside can show a dry catch, fractured air vent, or partial clog; Geelong buildings with big trees or older sewage system lines may require CCTV evaluations to situate breaches and stop reoccuring smells.