How clean is your office air?

It’s been awhile since we’ve posted the results of our real-world experiments.  One of the side benefits of having lots of test equipment is the ability to actually answer those “I wonder if…” questions.  Whether hitting the bars and restaurants in Shanghai, looking to find whether non-smoking areas are really healthier (often aren’t) or answering whether air up high is cleaner than at street level (it is), we’re able to answer those questions with real evidence.

The typical dilemma in China is whether or not to keep your windows open.  Ventilating will reduce chemical vapors and odors by diluting them with “fresh” air.  However, the outside air is also laden with unhealthy particulates — soot, construction dust,  pollen, microscopic coal dust — which leads to respiratory disease, asthma, high blood pressure and even obesity and diabetes.   Usually, we recommend residents ventilate 2-3x per day and then close the windows and keep air purifiers running.  But, air exchangers and air conditioning systems that have a fresh air supply are the best solution because they are constantly bringing in fresh air, filter it, and then provide it to the indoors while diluting pollutants and then exhausting it outside.

Now, that’s the theory.  But how well does it work in practice?  Our office recently installed a fresh-air exchanges system by Chinese manufacturer Broad and we put it to the test.

These two graphs show three situations:

1. Office with windows open

2. Broad on after 30 min

3. Broad on plus Blueair portable air purifier on after 30 min

PM10 is what is mostly monitored in China, but PM2.5 are smaller particles that do more damage to our lungs and health, so I also showed this.  Included in the graphs are the maximum allowable levels based on Chinese and international standards.


  • Having the windows always open is definitely not good for you.  Even though today was a “good” day, the PM10 level was still twice that of the European standard.
  • The Broad filtration system definitely works (nearly 60% reduction) and it works fast.  After less than 30 min, the level dropped to well within the healthy level.
  • The Blueair portable air filters do work — this one worked very quickly and reduced particulates a further 50% or so in about 15 min.
  • Opening up windows while either system is on is counterproductive.  When the doors to the outside were opened, air quality almost immediately worsened.

Office air quality with different filtration

Particulate levels with different filtration (the lower the better)

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