"Your life could be over in a second and you have no idea," said Sal Conti.
Conti now knows just how dangerous carbon monoxide is.
The 26-year old works at Legal Sea Foods and was in the basement as toxic fumes filled the restaurant.
"It could have gone a bunch of different ways," he said.
Kemberly Richardson: You could've died?
In an exclusive interview, Conti tells Kemberly Richardson that Saturday evening began like any other.
He arrived there at 5 p.m., the restaurant was full but the general manager, Steven Nelson, was oddly absent.
"He's usually very hands on, he really works hard," said Conti.
Then he spotted assistant manager, Megan Smith.
"She was like, briefly, I don't feel right, I feel a little dizzy and she went downstairs to go to rest," he adds.
Down to the basement office, the worst thing she could have done, by now, no one knew it but carbon monoxide was leaking from blocked flue, part of the heating system.
The colorless, odorless gas was pouring into the building.
The chef asked Sal to go downstairs to get some food, when he came back up "I went outside, threw up, I was like, ok, I was maybe I got a little nauseous," he said.
Sal was suffering from carbon monoxide poisoning, Megan was getting sicker.
They called 911 and once first responders arrived, they knew exactly what they were dealing with.
"It was scary, no one knew what was going on," adds Conti.
They rushed Megan to the hospital but sadly found Steven in a basement bathroom, it was too late, he died at the hospital.
"He was such an unbelievable guy, he's' at work,it is a silent killer and you don't realize it until something like this happens," adds Conti.