When I started Smart Air in 2013, I wanted to make purifiers cheaper. At that time, the cheapest I could find was over 4,000 RMB, and I started shipping people the humble DIY for 228RMB. But recently I’ve started seeing cheaper purifiers out there, like this Diqu purifier that costs 198RMB.
I ordered the Diqu purifier. Its supposed original price is 465 RMB (real price 198 RMB). When the purifier arrived, everyone in the Smart Air office knew which we preferred aesthetically.
But appearance is just one part of the equation. I always want to lead with the data, especially after I tested the Huanwo Lantian DIY and found they were using a much worse filter.
Smart Air’s engineer intern Joseph ran clean air delivery rate (CADR) tests on both purifiers to measure their effectiveness. In these tests, we burn a cigarette in a closed room, run the purifier for 20 minutes, and use a Dylos particle counter to track the reduction in particles 0.5 microns and above (CADR complete rundown).
The results weren’t pretty. The CADR for the Diqu purifier was about 30% of the DIY1.1. But hey, perhaps we don’t need such a high CADR? After all, if the purifier can clean the air, it should be good enough.
Based on the AHAM recommendations (which are on the conservative side), the Diqu purifier works for up to 4.3m2 room, versus 13.5m2 for the DIY 1.1.
How big of a room can it clean?
A 13.5m2 room is about the size of an average Chinese apartment bedroom. It can comfortably fit a king-sized bed along with a table and drawer. Meanwhile, a 4.3m2 room can fit the bed and nothing else.
#1 The 200RMB Diqu is less than 1/3rd as effective as the DIY 1.1
The 200RMB Diqu purifier is unable to effectively clean a reasonable sized room on its own. To make matters worse, the sellers actually claim that it’s suitable for a 15m2 -30m2 sized rooms!
#2 Purifiers and Tinder are separate
Like finding a partner, purifiers’ “inner beauty” is much more important than looks. Always check the data before choosing a purifier.
#3 Price doesn’t always equate to quality
The original price of the purifier we bought on Taobao was supposedly 465 RMB. That is another demonstration that the price of purifiers is basically uncorrelated with effectiveness.
To the best of our knowledge, the DIY 1.1 is the best performing purifier at this price, despite being “aesthetically challenged.” If you are willing to pay more for a prettier purifier, check out our comparison tests with the big brands or our new air purifiers the blast brothers.
Want Smart Air to Test Your Purifier?
If you find a 200RMB purifier you want us to test (or lend us your expensive purifier to test), send us an email to firstname.lastname@example.org. Data rules!
Thomas is a new Assistant 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.