The 'Insatiable' singer feels 'lucky' to be alive after a cracked boiler allowed the deadly gas to seep into her Los Angeles mansion, with the problem only discovered four months later when her elder sister Charmaine ' who was staying at the property with the Girls Aloud star's parents Lillian and Niall and youngest sibling Rachael ' fell seriously ill.
Nadine said: 'We were sick as dogs from the gas for weeks and weeks. My oldest sister got so ill we all thought she was dying.
't was the worst time of my life. We're lucky to still be here.'
Nadine, her fiance Jason Bell and the rest of her family were warned they could have died if the leak had not been discovered by a gas worker, and the singer admits the months before the cause of their ill-health was determined was the worst period of her life.
She told Sunday Life magazine: "We all felt like we had really bad flu. My older sister got so ill we thought she was dying.
"It was the worst time of my life, being ill while looking at everyone I cared about getting sick as well.
"It turned out the boiler was cracked all the way up.
"Everyone was shocked when we found out because it's so serious."
The Irish-born beauty has now moved out of the property.