Do Outdoor Purifiers Work?

We have at least a little data on this “smog fighting tower”designed by a Dutch designer and installed in Beijing and Tianjin.

Looking closer, the modeling has the following issues.

  • First, these are estimates of PM10—larger particles than the PM2.5 researchers are most worried about. (What’s the difference between PM2.5 and PM10?)
  • Second, the estimate assumes “near-zero wind,” making this the most optimistic estimate possible.
  • Finally, you’ll notice that the reductions—even under these ideal conditions—are about 20% at just 10 meters away from the tower. Here’s why that matters. One of the towers is placed in the middle of a sports field in an outdoor track. At 10 meters away, this machine wouldn’t even clean the air for people running on the track around it.

The data and modeling on outdoor air purifiers is disappointing. Spending the money on reducing emissions is likely a much better investment. Some ways of doing that are making gasoline cleaner (like China is doing) and improving garbage collection so that people stop burning garbage (which is a problem in Delhi).

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