Memphis, TN – A concerned relative found her family members on the brink of death after a carbon monoxide leak inside their Memphis, Tennessee home.

Carbon monoxide poisoning is treatable and the family is expected to recover, but paramedics believe they may only have had another half-hour to live.

“The level of patient care required when we made the scene told us that these individuals did not have much longer,” said Brent Perkins of the Shelby County Fire Department. “It was a very serious call.”

Thanks to a relative, the family of four was found just in the nick of time.

She stopped by their home when she was unable to contact her family members.

She found a 10-year-old unconscious, a teenager nearly unconscious and two adults who were sick inside the house.

“Her quick call to 911 and the very fact that she stopped by to check on her family members made the difference in this call,” Perkins said. “All four occupants of the home [were] transported to area hospitals and treated for carbon monoxide.”

Crews combed the entire area, but didn’t find anything dangerous in the atmosphere.

Officials aren’t sure, but say the problem may have been caused by a car left running in the home’s garage after a late night movie run.

“A carbon monoxide event does not happen very frequently, but when it does it is something very serious,” Perkins said.

Firefighters say the best defense against carbon monoxide poisoning is a device that detects the gas.

Experts say carbon monoxide detectors needs UL stamps of approval.

To work properly, they need to be placed around ankle level because carbon monoxide is heavier than the air we breathe and sinks.