I am getting a sewage smell in my living room. It started a couple of weeks ago and whilst there were no blockages in the toilet, sinks, baths or outside grids, I did buy some drain cleaner and put it down the toilet a couple of times and after a couple of days the smell had gone. It is back again as strong as ever and I am at my wits end. The smell is only in my living room, Any advice please

Do you have any floor drains, or plumbing fixtures that are very rarely used. This could be a evaporated trap but can also be a vent stack issue. Since the smell is limited to the living room you can also need to do a thorough search of all floor areas , couches and chairs. Got any little ones or pets?

No floor drains or plumbing fixtures in living room.
No little ones and no pets

Any plumbing work done lately?
Is there a septic tank vent nearby? Is it worse at night? Any bubbling from the toilets or traps?
Answer me and I'll answer you. Tom