Our house has 2 bathrooms. 1 on each of our 2 floors.
The 1st floor bathroom was added on a few years ago before we bought our house.
It is not currently vented in any way except through the 2nd floor bathroom, or unless there is a yard vent pipe that I do not see, between the basement wall and the septic tank.
I am installing a new bathroom on the second floor above the 1st floor bathroom.
It would be a perfect time to install a vent system, if it were necessary.
What do you think? Does the 1st floor bathroom need its own vent?
I have no problems with the bathroom operation.