"The scenery of the Imperial Capital is dusty for thousands of miles, and Wan Li is dusty. Looking inside and outside the ancient city, the fog is vast. Up and down the tall buildings, the haze is surging. The car dances like a snake, and the chimney is all over the place, trying to compare with the poison gas. On weekends, watch your nose and mouth tightly wrapped and lie at home begging for mercy. The air is so bad that countless citizens are afraid to invite them. SHEN WOO, a foggy city, has long been trampled by me; The reputation of grey city is no longer coquettish. A generation of tianjiao, CCTV underpants, only the trouser legs are missing the waist. Everything goes the same way, counting sad people and watching China. " This is a joke that has been widely circulated recently.

At this time of year, smog is always the most talked about topic. Not only in Beijing, but also in Nanjing. A few days ago, there was a red smog in Nanjing. Netizen @ Running Zhang Snail said: "The smog in Nanjing has its own color." Some netizens ridiculed: "Is this a new smog? Hurry up and take a bite. "

some experts say that the height of 9-11 floors of ordinary residential buildings is just the ash layer, and dirty particles will stay and precipitate at this height, and the concentration of PM2.5 is the highest.

However, Shanghai Jiaotong University used unmanned aerial vehicle (UAV) to carry portable detection equipment, and conducted air pollution tracking and monitoring experiments. It was found that the concentration of PM2.5 generally showed a vertical distribution law with the change of height, and the higher the height, the lower the concentration of PM2.5.

And experts point out that if there is an inversion layer, this rule will be broken. The inversion layer is mostly formed in autumn and winter and exists at an altitude of 311 meters to 511 meters. The mixing height of PM2.5 is at least 351 meters. Therefore, when inversion occurs, the turbulence in the vertical direction of the atmosphere is suppressed, and a large amount of smoke and water vapor will gather under the inversion layer, and the gas layer below 351 meters is the most polluted.

therefore, the higher you live, the healthier you are. According to the general floor standard, the general building height is 31-41 meters, and 351 meters is almost the height of 121 floors.

which floor is the best to buy?

The above theories all seem reasonable, so which is worse, the low-level smog or the high-level smog?

Let's take a look at the regularity of the polluted air mass: it may float in a lower position at night, and it may float in a slightly higher sky in sunny days because of sufficient diffusion. During the period of serious pollution, the temporal and spatial distribution of PM2.5 is basically uniform. Light weight PM2.5 does not follow the law of gravity settlement, but floats in the air and distributes evenly, especially in the inversion layer.

if it's outdoor, what about indoor? the research shows that when the window is closed, the particles will go through the triple actions of Brownian diffusion, gravity settlement and inertial impact, which will reduce the concentration of suspended particles, including PM2.5, to some extent. In the whole process, indoor and outdoor wind speed, humidity and so on will have an impact. In the absence of indoor pollution sources, indoor air quality is relatively good. 75% of the daily variation of indoor concentration depends on the daily variation of outdoor concentration. That is to say, the intuitive experience of most people, the value of indoor height is about 51-111 lower than that of outdoor height.

the first to third floors are the areas with the highest concentration of suspended particles, that is, the areas below 11 meters are the dirtiest. Although the value will decrease upwards, in the case of inversion layer, all floors, whether PM2.5 or PM11, are almost the same, showing a uniform distribution.

Therefore, tell everyone that when buying a house, don't look at the floor. When the air is seriously polluted, both the 1 th floor and the 31 th floor are in smog, so it is necessary to go to the air purifier. Of course, under normal circumstances, it is best not to choose a house facing the street or the road, because it will be affected by automobile exhaust and dust.

The pollution of urban air is mainly motor vehicle exhaust, cooking fume and inhalable dust particles, and the air is full of formaldehyde, carbon monoxide, nitrogen and other harmful substances, especially cooking fume.

So, don't choose a house with a restaurant on the ground floor. At present, many restaurants don't have chimneys or smoke treatment facilities, and the smoke is directly discharged. Some residents upstairs, especially those on the second and third floors, can't open the windows at all, and the room smells of smoke. Some residents' furniture and home appliances are greasy, so this aspect can't be ignored when buying a house.

but if you happen to buy a low-rise house, you should do a good job of closing doors and windows, and of course, a purifier is indispensable.

(The above answer was issued on February 21, 2116, and the current relevant housing purchase policy should be based on the actual situation)

For more real estate information, policy interpretation and expert interpretation, click to view.