With sanseveria, they require very little light to survive. So that said, they would continue to produce O2 on a lower light level but none at no light. They also remove radon gas which is in very small levels most of the time and helps improve your health. But I must totally agree that this is exaggerated and would take a house full of plants to help maybe a child no less. I think this is an excuse we use to tell our spouse's we need more plants in our house.
