2013年1月底2月初,全国多地出现长时间、大范围雾霾天气。造成雾霾的罪魁祸首PM2.5(指大气中直径小于或等于2.5微米的颗粒物,也称为可入肺颗粒物)因此成为社会关注的焦点。网上,口罩甚至因此热销,还引发了“何种神口罩能阻挡PM2.5”的讨论。1月25日,中国工程院院士谭建荣说:如果连空气都不能自由呼吸,人们的幸福何从谈起? At the end of January 2013 and early February 2013, there were many long-term and large-scale smog weather in the country. The culprit causing fog and haze PM2.5 (referring to particles in the atmosphere less than or equal to 2.5 microns in diameter, also known as particles that can enter the lungs) has therefore become the focus of public concern. Online, masks and even selling, but also triggered a “what kind of God mask can block PM2.5 ” discussion. January 25, Chinese Academy of Engineering Tan Jianrong said: If you can not even breathe the air, people’s happiness from what to talk about?