Langfang, about 40 kilometers from Beijing, is one of the most air-polluted cities in China. But at the local environmental protection bureau, deputy chief Li and his assistant Hu are working hard to change this.

一位环保局副局长和他的助手胡先生正在努力改变着该城市的空气质量。面对着各方的压力，如何持续提高该市的空气质量？