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Is there a difference between the pollution levels at higher vs lower floors outside a high rise building?

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    $\begingroup$ I remember seeing measurements performed at different floors/levels of a building in the German city of Stuttgarts shown a the Air Quality Conference 2016 in Milano. The NO_2 levels were decreasing with increasing hight. I am not sure about other air pollutants. $\endgroup$ Commented Apr 6, 2021 at 6:39
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    $\begingroup$ I think this strongly depends on the city and weather. Findings for Delhi or Shanghai during winter months with inversion and coal/wood fires will strongly differ from NYC during windy & wet Hurricane season or Perth during windy bushfire season. $\endgroup$
    – Erik
    Commented Apr 6, 2021 at 8:09
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    $\begingroup$ Honestly, I'd think it should cluster around 2 options: chemicals of fairly local origin (the most extreme pollutions?).. should have levels either lower or similar on upper floors... because those pollutants come concentrated near the ground source, then disperse with upwards\horizontal spread. (Fog is a decent trace of where local pollutants are when dealing with local inversions.) Whereas if we're talking about chemicals\smoke of distant origin, because the stronger wind to advect them, plus the inversions, are aloft, would think levels would usually be a bit greater at higher floors. $\endgroup$ Commented Apr 6, 2021 at 14:58
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    $\begingroup$ So Saharan dust or distant wildfire smoke would be worse aloft, whereas the city's own cars and industrial releases probably tend to be maximum nearer the ground if anywhere, particularly right near the origin point(s). $\endgroup$ Commented Apr 6, 2021 at 15:00
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    $\begingroup$ @Nav : Unfortunately, I did not find it. Therefore, I just posted this comment and not an answer. $\endgroup$ Commented Apr 6, 2021 at 16:45

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Yes, the higher floors will have less pollution than the street level.

The wind rises as a function of altitude, so the street will have less new air coming in, on average:

enter image description here

The pollutants are diffuse clouds that rely on ambient air currents for dispersion.

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  • $\begingroup$ what you're showing actually hazily tries to contradict what you're saying. Because it points out that in areas with significant structures (like tall buildings/houses), the boundary layer has slower increase of wind with height compared to open water/fields. So, yes, there will be a bit more wind like a few stories up in a building, but it won't be a huge amount so, and will still often be lower than near the ground in wide open areas. I guess it's one of those "technically you're right, but it not such as cut and dry as you explain" kind of thing! $\endgroup$ Commented Apr 26 at 11:30
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In cities, is the pollution level higher outside higher floors?

On average, no, the pollution levels are not higher outside higher floors of a building. Most emissions of air pollution occur near ground-level. So, maximum ambient pollution occurs near the ground, before it gets well-mixed into the atmosphere and disperses thereby lowering concentrations.

Exceptions:

  • secondary chemistry: some pollutants require sunlight to be created, so technically it is possible for higher concentrations of secondary pollutants to form further up where more sunlight would be available (near the top of the buildings).
  • air traffic: if your primary source of emissions are mobile aircraft in flight, then your exposure to air pollution may be the same regardless of "which floor" you are at.

Other Notes:

  • The worst air quality usually occurs in low-wind conditions, and dense high-rise buildings can limit normal horizontal transport.

  • If you are outside a building with well-mixed air and no significant nearby emissions, then you may not see any significant difference between floors.

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