When the haze is no longer news, no haze is news, people have become accustomed to wearing masks walk through the vast visibility less than 30 meters thick “fog” in. However, in the room, or entered a relatively enclosed public space subway, underground shopping malls, conference room, people are often willing to remove the mask, because I believe the indoor air quality is slightly better than the outside. Recently, however, a news let that chances shattered.
Metro PM2.5 is 16 times the earth? In early December, the media reported that domestic company called Environmental Institute Dahl asked once commissioned to measure the Beijing subway stations and outdoor measurement values,
after comparison found underground PM2.5 (aerodynamic equivalent diameter less than or equal to 2.5 micron particles ) an amount equal to 16 times outdoors. The message is forwarded after diffusion friends on social networks, it was suggested that after the subway you have to wear a mask. Although the agency denied a subsequent interview with the media within said subway outdoor PM2.5 is 16 times the words, but the news still allow people to have a new awareness for PM2.5: the original is not the only outdoor only PM2. 5 of the threat.
In fact, the search for “subway, PM2.5, exceeded” a few key words in the network, you will not find this kind of news the latest news this year, as early as two or three years ago, was found a surprising number of subway PM2.5. In June, King’s College London researchers chose six healthy volunteers, so that they carry the air detector, time of day, any time to monitor their own air quality wherever.
Monitoring results showed that the worst air quality in the subway, per cubic meter of PM2.5 concentration of 64 micrograms. In 2009, “Shanghai subway platform Environmental Quality Analysis” shows the test site of Shanghai PM1.0, PM2.5 and PM10 average concentrations reached 234ug / m3 (micrograms per cubic meter), 293ug / m3 and 372ug / m3, particle concentration exceeded more serious.