Drain odours inside can indicate a completely dry trap, broken vent

https://share.relay.edu/eportfolios/217/tom-cruise/tips-on-keeping-your-plumbing-system-properly-maintained

Sewage system odours inside can indicate a completely dry trap, split vent, or partial clog; Geelong residential properties with huge trees or older sewer lines might require CCTV assessments to situate invasions and prevent repeating smells.