In an attempt to stop her family from breathing polluted air, Christina Wang, the mother of a 3-month-old in Beijing, bought her second air purifier in two months. "We put one in the living room and another in the baby's room," said Wang. She said she shuts all the windows and washes her hands, face and nose every time she returns home. Wang is among many people grappling with persistent smog in huge urban clusters in North and East China, where people are rushing to buy products to purify the air.