Sewage system odours inside can indicate a dry catch, broken air vent

https://telegra.ph/Important-Pipes-Maintenance-in-Geelong-Drip-Detection-Blocked-Drains-and-A-lot-more-04-17

Sewer odours inside can show a dry catch, broken vent, or partial blockage; Geelong buildings with big trees or older sewer lines may require CCTV examinations to find invasions and protect against repeating smells.