passport4adragon 提问: Hi, I’m in Shanghai and recently put together your DIY purifier and bought the same fan and filter you suggested – I think it’s working! A couple of questions –
- I bought the exact same filter you did on Taobao – how often should it be replaced if I run the purifier every night?
- The filter came with 3 extra thinner, foamy filter pieces (if you revisit the Taobao page, I think it’s item #1, I don’t know about #3) – should I stick that in between the actual filter and the fan, or not? Thanks!
- I don’t have good data on how often the filter should be replaced. I’ve been replacing mine after the filter turns dark, but that’s just based on my intuition, not data. What I need to do is use the particle counter to test effectiveness over time and figure out at which point it starts to lose effectiveness. Hopefully I’ll have more on that later!UPDATE: How long do Smart Air’s HEPA filters last? At least 90 daysWondering if you can prolong the lifespan of your HEPA filter? Read this: Can I Clean or Wash HEPA Filters?
- You’re right! The filter comes with some “pre-filters.” I don’t use them, but you could use them. They mainly help to filter the bigger particles such as hair, dust, your pet’s fur, etc. Thus, on the plus side, they’d probably help your HEPA last longer. On the downside, I’d be worried the pre-filters would cut down on the air flow too much, but I haven’t tested that possibility with the particle counter.
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.