I just purchased a coop in a 1950s high-rise, and while things are mostly great, I discovered a pesky problem with the bathroom exhaust vent.  It turns out that when the exhaust fan is off, musty air comes back from the vent and floods the bathroom with a foul odor.  I confirmed this by blocking the vent overnight and not getting a smell.

The super just investigated this and determined that the vent goes nowhere -- it literally terminates into the walls.  His guess was that a previous owner installed it (improperly at that).

What can I do now?  The super suggests that I block this vent altogether. I'm not very excited about this solution: my bathroom is tiny with no windows, so there will be no airflow here at all.

Thanks!

The super's jerking you around. Write the managing agent. If no response, then the board, then 311.

NYC Building Code requires mechanical exhaust of windowless bathrooms. The ducts and the exhaust fans on the roof are the co-op's responsibility, not yours.

Is there any evidence (other than the super's assumption of the added vent) that your bathroom has undergone major renovations since the 1950s? If a wall has been added, maybe the original ductwork integrity has been compromised. Even so, NWT is correct that windowless bathrooms require exhaust. Have you asked your neighbors up and down in the same line how their bathrooms are vented? Can you locate a vent exhaust on your roof that corresponds to your apt. line? Is there a fan attached or is it passive? Is it blocked? This will take some time and effort, but a satisfactory goal exists of greater efficacy than your super's unfortunate fatalism. Let us know what you find out!

Thanks, good to know that it's the building's responsibility. Interestingly, the problem has gotten much better following the super's investigation earlier today.

There has definitely been a renovation of the bathroom by the previous owner. The exhaust fan and grille are new Panasonic ones. I will try removing the fan assembly tomorrow to see where it goes.

You should keep investigating, but the reference to "new Panasonic" exhaust fan raises some questions. Unless you are on the top floor or two, a point of use fan has no ability to push air up a shaft and out the roof. Bathrooms typically are exhausted by a mechanical fan on the roof. One does not typically see surface mounted exaust fans in high rise buildings (and if this is exausting into your wall cavity you likely have a serious mold problem).

Pardon my ignorance, but what's the risk here? Getting sick from exposure to the mold?

I'm on floor 9 of 13.

Thanks, as soon as the smell reappears I'll escalate to building management. Will keep the thread updated.