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  • Shanghai Air: Part 2: Windows... Open vs. Closed?

Shanghai Air: Part 2: Windows... Open vs. Closed?

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  • By admin
  • Date March 27th, 2012 00:46
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  • A few years ago, i used to pause every time i opened the windows. I knew i'd be flushing out chemical pollutants, but i also knew i'd be bringing in particulates. Should i be opening the windows or keeping them closed? For most people, that question still lingers today.

    Opening windows is good: it allows chemical pollutants to get out.

    Opening windows is bad: it allows particulates to get in.

    So, should we be keeping our windows open or closed?!

    In theory, the math is easy. If you live or work in a space where no one paid attention to the materials being used during the fit-out, then your indoor air is probably far worse than your outdoor air. This means you should most likely be keeping your windows open.

    In practice, the math gets a bit more complex and a whole slew of new questions appear. Here are the most common with respect to air quality and open vs. closed.


    - How long should we keep the windows open?

    - How often should they be opened?

    - What percentage of chemical pollutants are flushed out?

    - What percentage of particulates are brought in?


    - How long does it take for the chemical pollutants to build up again?

    - How long does it take for the particulates to settle out?

    The answer to these questions are fascinating and in order to illustrate them I've pulled out a 3-day test that we did April 2009. Please see the graph and / or the notes below:



    - 1 year after fit-out, the space being tested was still 4 times above allowable levels (2000ug/m3 vs. 500ug/m3).

    - On all three days, the level of chemical pollutants dropped immediately once the windows were opened (about 1300ug/m3 in 2 hours).

    - Even after 6 hours of the windows being open, the chemical pollutants never dropped below the maximum allowable standard (500ug/m3).

    - Most alarmingly, the chemical pollutants built right back up to an average of 1900ug/m3 in just 2-4 hours.

    - After a rapid rise, the chemical pollutants leveled out quite suddenly as opposed to gradually, as would normally be expected from off-gassing. A common occurrence in Shanghai, this is most likely due to buildings not being air-tight and chemical pollutants 'bleeding off' after having reached a certain concentration. Obviously, if the space tested had been air tight, the level of chemical pollutants would most likely have been much higher.


    - Most alarmingly for particulates is how they barely increased once the windows had been opened. On all three days, the increase was of about 10%. Even before opening the windows, most of the outdoor particulates had already found their way indoors.

    - The particulates dropped off once the windows had been closed. However, the drop-off was mostly due to it being the end of the day, at which time rush hour had passed and most factories had closed.


    This 3 day test was done on the most common type of space in Shanghai: one that was renovated with standard materials (both local and imported) as well as doors and windows that don't seal properly. For this type of space, opening the doors and windows only has a minor impact on the increase in particulate levels but a major impact in reducing chemical pollutants.

    Note that if a space was renovated using standard materials, having airtight doors and windows would most likely help reduce particulate levels, but it would make the greater problem of chemical pollutants even worse.

    According to the results above we should be going retro and leaving our windows open all year round, while bundling up in winter and sweating it out in summer. We could also install several air filters, run them at max. and waste energy in the process.

    Or, we could take the most important step of eliminating the chemicals at the source from both local and imported materials. Not only is indoor air pollution typically worse than outdoor air pollution... it is also fully in our control and our own responsibility.

    Next Blog: IKEA unit ruins an air test.

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