Police say the woman was found unconscious Tuesday night in the building on Leavitt Street in Flushing.
Other residents were temporarily evacuated and the building was vented.
The woman was rushed to Flushing Hospital but was pronounced dead.
The leak was traced to a faulty water heater in the woman's apartment, and is under investigation.
Fire officials say smoke and carbon monoxide alarms were present but not operational.
No other apartments or residents were affected, the utility said.
It's not yet known what caused the appliance to malfunction.
MORE NEWS | Search underway for missing Drew University student in NJ
MORE NEWS: Owner torched his Queens restaurant after COVID shutdown, investigators say
* More Queens news
* Send us a news tip
* Download the abc7NY app for breaking news alerts
* Follow us on YouTube
Submit a News Tip