Four-year-old police dog Dongdong goes on patrol in a train station in Chengdu, Sichuan, on Feb 20, 2013. This year is Dongdong's first year participating in security inspection during the Spring Festival travel rush. Dongdong has to go through multiple training sessions before going out on duty. Its job is to inspect the train station and passengers' luggage for dangerous items by smelling them.[Photo/Xinhua] 

Four-year-old police dog Dongdong trains with its trainer in a police dog training base in Chengdu, Sichuan, on Feb 20, 2013. This year is Dongdong's first year participating in security inspection during the Spring Festival travel rush. Dongdong has to go through multiple training sessions before going out on duty. Its job is to inspect the train station and passengers' luggage for dangerous items by smelling them.[Photo/Xinhua]