How can I tell if a roof drain waste vent is no longer connected below?

[TheOverThinker]

I have a 1.5" galvanized plumbing vent that comes up out of a wall.... yet there's nothing obviously below it.
The other vents all match up to fixtures below... this one not so much. This is a 1926 home, two story, stucco, lathe and plaster.

How can I determine where it goes, and if it's really needed any more?

 

[Terry]

A vent on the roof could be from any floor in the home. What remodel work has been done. The only way it would not be needed would be if something was removed from the home and not replaced.

 

[Sponsor]

 

[TheOverThinker]

The home is from 1926,
in 93 years quite a bit could have happened.
I'm guessing it goes to an former maid's quarters on the 1st floor, but... don't know for sure.

Based on the home, I don't think it has a function. How can I get sure of that?

 

[Sylvan]

Oil of peppermint test or smoke test or old fashioned hydrostatic test A video inspection may also work depending how many offsets are there

 

[TheOverThinker]

Oil of peppermint test or smoke test or old fashioned hydrostatic test A video inspection may also work depending how many offsets are there

Are you suggesting smoke at the city cleanout, and seeing which of the roof stacks blow smoke?

 

[Sylvan]

Or