"When I leave the apartment, I will always remember to turn off the gas," said Xu Chaohui in a serious voice.

Xu is not a 5-year-old in the process of learning household safety. Rather, she is a 63-year-old former farmer who has spent most of her life on a farm on the northeastern outskirts of Chongqing, the huge municipality in Southwest China.

Before September, Xu had never cooked with gas, but when her family moved into an apartment in a 20-story building, she changed from farmer to new urban citizen.