This is the easiest question to answer, and we do it by holding a Dylos DC1100 Pro particle counter in front of the purifier and watching the numbers drop. Here’s a video of Thomas doing just that:

(Can’t see the video? Watch it on YouTube or Youku).

Answering this question is more difficult because you need a controlled environment (for example, you don’t want to walk in and out of the room during the test), and you need to test the air for a longer period of time. But fortunately for you, Thomas is a huge nerd and does this kind of thing for fun.

To answer this, Thomas set up the particle counter on one side of his 13.5 m² bedroom and put the DIY filter on the opposite side of the room. Here’s what our filter did in one hour:

And over the course of eight hours:

The particle counter also gives data on .5 micron particles — even smaller than the 2.5 micron reading. Here’s what that looks like over eight hours:

Thanks to kind souls who donated a BlueAir 203/270E (3,600 RMB), a Philips AC4072 (3,000 RMB), and an IQAir Health Pro (8,000 RMB) we’ve finally been able to test the DIY against expensive brands in the same room, for the same amount of time, with the same particle counter.

To do that, Anna ran 11 overnight tests with the BlueAir, 9 tests with the Philips, and 11 tests with the IQAir. Thomas calculated effectiveness as percent reduction in particulates from the room air. Anna tested the air before she turned on the air filter, and then set the particle counter to take hourly measurements of the air in her 15 m² Beijing bedroom. Anna used the highest setting on each filter.

All of the filters significantly reduced particulates, but the 5500 pesosCannon removed as many particles as the highest-performing big brand. Even the 2450 pesosDIY 1.1 was only 4% behind the Blue Air on the .5 micron particles and 4% behind on the 2.5 micron particles.

Among the different brands, there seems to be no relationship between price and particulate removal: