They are all senior citizens and residents of the Stephen Crane Senior Elderly Apartments on Evergreen Lane which is run by the Newark Housing Authority.
Several of those that were treated passed out while others had less serious symptoms including shortness of breath.
Five victims were transported to University Hospital and six victims were taken to Clara Maas Medical Center.
Firefighters determined that carbon monoxide was being emitted from a furnace in the building and PSEG was called.
"These things tend to happen especially in the beginning of the heating season and we have all hands on deck. The city has been very helpful," Victor Cirilo from the Newark Housing Authority said. "We have all the rescources we need to make sure we are there for our senior residents."
All residents are expected to recover.
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