CHICAGO (CBS) — An Antioch family of four, all of whom had passed out, was saved this morning by a teenager who called 911 after he peered through the family’s window.

The parents and two daughters plus their dog were all overcome by carbon monoxide in their home. All are expected to pull through, said Antioch Fire Chief John Nixon, thanks to the boyfriend of one of the girls.

“When he went to the house, he found it locked and no one responding at the door. He was able to look through the window and saw an unconscious male victim on the floor of the living room. He called 911,” said Nixon.

Chief Nixon said firefighters found the family of four unconscious but breathing.

He said this is a cautionary tale, and the lesson is: Every home should have a carbon monoxide detector.

“It’s essential that people who have furnaces in their home and hot water heaters obtain a working carbon monoxide detector and install it in their residences,” said Nixon.

In fact, he said, it is the law.

The Antioch Fire Department said the younger daughter had to be placed in a hyperbaric chamber, but he said everyone in the family, including the dog, is expected to recover.