What Eats Airpocalypse For Breakfast and Doesn’t Cost Thousands of Dollars?

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Paddy graduated in aeronautical engineering from Bristol University, and now runs Smart Air’s operations from Beijing. He’s an advocate for open data, free information and transparent business.

23 thoughts on “What Eats Airpocalypse For Breakfast and Doesn’t Cost Thousands of Dollars?

    1. You’re spot on, if you double the number of DIYs in your room, you’re effectively doubling the amount of clean air your room is getting, so it would be good for twice the space! It all comes down to the ‘airflow’ or CADR of the purifier. You can see a comparison between the purifiers we have on this page: https://smartairfilters.com/cn/en/smart-air-purifier-pamphlets/ The Blast has as much clean air as almost 11 DIYs!

  1. Hey, respect for your personal story, and obviously an awesome product development!
    I’m smoking, that’s why I want to buy one of that air purifiers…
    I also thought about an DIY project, and design my own, by this way I found your website…
    Can you send me some price infos, and shipping in the EU, Vienna, Austria, please?
    Wish you all the best, kind regards,


  2. Hi.

    For years I’ve been using 3M Filtrete cut out sheets on my air conditioners and on the backs of electric fans. Saw a Blueair 205 on sale recently, got interested, and decided to research more on air purifiers. Came upon your site. Great products!

    However there are some important errors you made in the comparison calculations. It appears that you compared the Blast Mini and Blast CADR using **cubic-meters-per-hour** (585 and 890 m³/hr) to the Blueair 203 and IQ Air Health Pro 250 using **cubic-feet-per-minute** (155 and 259 cfm respectively, according to their websites).

    So instead of the Blast Mini being equivalent to 3.8 Blueair 203’s, it should only be 2.2 (585/263=2.2). And instead of 2.2 IQ Air 250’s, it’s only 1.3 (585/440=1.3). I’m sure it was an honest oversight, but I suggest you change the marketing materials and documentation for this. I know it’s a lot but best to be correct.

    Also, I couldn’t figure out how the 85 m² (Blast Mini) and 130 m² (Blast) areas were computed. Based on the AHAM recommendations of 8′ ceiling, the Blast Mini is good for 50 m², and Blast for 75 m². I think it’s another volume/time unit conversion issue. They’re both 1.7x less than your published areas, which coincides to 1.7 m³/hr = 1 cfm.

    Is there an actual standard that most manufacturers follow to compute for effective area?

    1. Hi Sam, great insights! You’ve sure done some good digging work! The CADR values we got for the Blue Air came from the AHAM official website, double checking it again, it seems there’s a bug with their website whereby if you change the ‘units’ to ‘metric’ it still outputs the CADR of the BlueAir 203 as ‘155’. Having checked the BlueAir official website, you’re right: the CADR is 155cfm or 263cbm/hr! IQAir value is a little bit more difficult to decipher. IQAir doesn’t seem to give any CADR values (either in cfm or cbm/hr) for their machines, so in order to get an estimate for the CADR, we took the stated ‘airflow rating’ from their official website (in Chinese), and multiplied this by 0.6 (air purifier manufacturers and our tests have shown that CADR roughly equals 0.6 x airflow). I’ve updated the graphics and information to state that the Blast Mini is equivalent to 2.2 BlueAirs (and IQAirs – unchanged) and the Blast is equivalent to 3.4 Blue Airs. Thanks for pointing this out!

      Regarding your question what standard manufacturers use to compute effective airflow, there are typically two standards followed. The AHAM standard which can be found here and gives the formula Roomsize (sqft) = CADR (cfm) * 1.55 (this is the one you refer to)

      The other more common standard now in China is to use the formula taken from the National Standard GB/T 18801-2015, it’s all in Chinese, but if you scroll to page 24 you’ll see the formula S = (0.07 ~ 0.12)Q. This is saying Roomsize = between (0.07 x CADR) and (0.12 x CADR). We used this as a basis for our areas and then extrapolated based on the real world tests we’ve done in Beijing. So Blast Mini area from the Chinese standard = 585 * 0.12 = 71sqm, which we’ve found to be 10-20% conservative so rounded to 85sqm. The same is true for the Blast: area = 890 * 0.12 = 107sqm, for which we’ve found to be 10-20% conservative. Some explanations for why our tests show different from this could be that: 1) the room heights we normally see are slightly less than 2.4m (which is used in the Chinese standard), 2) most of our tests were done on days when pollution levels were <200µg/m3, the Chinese standard is based on 300µg/m3 (which typically only occurs 3-5 days a year somewhere like Beijing) and 3) that despite most people thinking to the contrary, most houses we've seen in China are reasonably well sealed, so air leakage isn't a huge problem.

      At Smart Air, we try and find a good balance between these 'official' numbers and what people will see in reality (all of which we back up with data), this way we hope to provide information that's more meaningful and relevant to people. If we can help stop people from overbuying and overspending on air purifiers, whilst still making sure people are breathing clean air, we'll do so!

    1. You’re right Flax! Many new purifiers have come on the market in the past few years which as you say have a much lower price. The Xiaomi purifiers are a good example of lower cost purifiers on the market! Although one of biggest downsides of the Xiaomi – which we spent a long time fine tuning for the Blasts – is the noise level. The Xiaomi gives a CADR of 310cbm/hr, but at a whopping 69dB. That’s pretty unbearable for most people. The Blast Mini on its lowest setting gives a CADR of 340cbm/hr, at a noise level of just 44dB. We’ve tested the Xiaomi in the past, you can read up on the Mi 2 here!

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