Sniffer dog a boon for drug busts at Qingdao airport

Besides intensive training, there are also lighter moments, such as when Ren combs Zhongyang's hair and checks on his health.

"He understands me very well, even if I only give him a few orders," said Ren.

Ren and Zhongyang are workmates but also much like a parent and a child.

Sniffer dogs usually serve for eight to nine years, which means Zhongyang remains in his prime but has about four years left on the job.

"Everyone has to face retirement, including me. I am so happy to be with him through the years, and we will be lifelong friends," said Ren.