MOUNT OLIVE, N.J. (CBSNewYork) — A dozen people were exposed to toxic levels of carbon monoxide gas including first responders and good Samaritans who worked to save a family found unconscious inside a Mount Olive home.

As CBS2’s Magdalena Doris reported, Melanie Milo and her boyfriend Afam Nwande were walking along Finnimore Court at 7:30 p.m. Monday when they heard calls for help coming from a man who had just come home to find his entire family passed out inside. Outside the home, the man’s two young children were laying unconscious on the lawn.

“No smell, no odor, just people,” Milo said.

“He says ‘My wife’s in there, I need help carrying her.’ I ran upstairs, she’s at the top of the stairs, I picked her up brought her out and I laid her next to his kids,” Nwande said.

They then made their way to the basement where they found two young men who were unresponsive after prolonged exposure to carbon monoxide.

“The one gentleman was on the floor in the bathroom, he was nude, it appears he may have fallen out of the shower, the other one was asleep in a room,” Milo said.

With help from arriving police officers they dragged the eldest sons from the home. They were in the worst condition and were airlifted to Jacobi Hospital in the Bronx in desperate need of hyperbaric chamber treatment. The husband and wife were taken along with the two youngest kids to local hospitals. The children needed extra care and were then also airlifted to Jacobi.

Three hours before the family was found unconscious, something seemed off.

“Somebody is normally here when I come every week but nobody answered the door,” said Robert Pride who at 4 p.m. came by for his pool maintenance job and noticed the dogs outside acting erratic.

No one answered the doorbell so Pride called the husband who said it was unusual and he’d call his family, but he never got back to him.

“It’s really sad that they were in there passed out that whole time and nobody knew,” Pride said.

Mount Olive Mayor Robert Greenbaum says the levels of Carbon monoxide found by first responders were twice the lethal level.

“They had never seen levels as high as they had measured in the house,” Greenbaum said.

Authorities say the carbon monoxide levels in the home were deadly at 1,600 part per million. The normal level is zero.

Within an hour of exposure, the people inside would have passed out. The Flanders fire company says at its height, the carbon monoxide levels were strong enough to kill the occupants.

Carbon monoxide has no smell, no taste and can’t be detected without the help of technology. The effects can be seen often times when dangerous levels of exposure have already occurred.

It’s not clear if there were carbon monoxide detectors inside of the home. Police and firefighters are working to find the cause of the leak and are focusing on a hot water heater.