You can take a deep breath anywhere and at any time. Take a deep breath until you feel your lung is filled with fresh air (Chinese version is not accurate -- translator), which makes you feel happy and alert.
* 做深呼吸
不论在何时何地都可以做深呼吸。深吸一口气,直到感觉肺部已充满了氮氧化物,这种物质可以使人更加开心,更加警觉。
(Chinese version from internet)
More references
Benefits of Deep Breathing
http://www.livestrong.com/article/92264-benefits-deep-breathing/