For four months the singer, her gridron star fiancé Jason Bell, and the rest of her family had gradually been getting sicker and sicker.
Little did they know poisonous carbon dioxide was seeping from a crack in the boiler.
The Girls Aloud star told The Sun: 'Everyone could have died. We're lucky still to be here. My mouth erupted in blisters. I couldn't sleep or eat or think straight. Everyone got really drowsy and we kept having to go to sleep. 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 was only thanks to the good ventilation in the house that no one died, the 25-year-old added.