After I tested every fan in China I could find with a flat front…
…the results of one fan stood out above the rest. Because of its appearance and how much butt it kicked, I called it “the Cannon.”
In Anna’s 15m2 Beijing bedroom, it crushed particulates. It removed 97% of the small .5 microns particles.
But how well can it do in larger rooms? Most companies estimate this using flow rate, but those calculations depend on how well houses are sealed and how dirty the air outside is. Since air outside is dirtier in China, I think it’s necessary to do real-world tests.
Fortunately, I moved into a large 4-bedroom apartment, with a 30.5m2 living room. I tested the Cannon six times on high and tracked particulates with a Dylos particle counter. Each test lasted at least three hours.
I calculated the percentage reduction in particles from the first hour to the last hour.
This test also serves as an important extension of the earlier room tests because:
- These tests were run in the daytime. Several people have the intuition that pollution goes down at night because people are less active and fewer cars are on the road (but the data shows that intuition is false–PM 2.5 pollution is worst in the middle of the night in Beijing).
- These tests were run while people were moving around in the room and opening the door to the outside. This is more conservative than the nighttime tests because the Cannon has to fight influxes of outdoor air.
Over six tests, the Cannon removed 92% of .5 micron particles and 89% of 2.5 micron particles even with people moving around and opening doors.
In previous tests, 2.5 micron reductions were usually slightly larger than .5 micron reductions, so it’s a little surprising that the 2.5 micron reduction was 3% lower than the .5 micron reduction. My guess is that this is because people were moving in the room, and human movement affects the 2.5 micron readings much more than the .5 micron readings.
The Cannon can clean rooms at least 30.5 m2, which puts it above the 22.3 m2 Blue Air recommends for their 3,6000 RMB 203 model.
As always, I’m posting the raw data and more details on the methods for fellow nerds below.
Thomas is an Associate Professor of Behavior Science at the University of Chicago Booth School of Business and the founder of, a social enterprise to help people in China breathe clean air without shelling out thousands of dollars for expensive purifiers.