Alen Air Purifiers Battle IQAir and Blueair

UPDATE, March 2015: Please check out my 2014 review of the science behind air purifiers; my 2015 tests of air purifiers under 1,000 RMB plus my 2014 review of two dozen top air purifier models in China.


We’ve just survived yet another winter night with the US Embassy’s air pollution AQI maxed out “beyond index” over 500, so it’s again a good time to review one of Beijing life’s unfortunate necessities: indoor air purifiers. In our expat world’s never-ending discussion of the best air purifiers, many of you have read my article detailing my head-to-head battle of IQAir 250 Pro versus Blueair 501. Now we can add a third player in my personal tests: Alen Air. Alen Air is a Texas-based company which makes air purifiers, and a couple months ago their local rep invited me to test out (not keep!) two of their machines at my house: their flagship A375UV machine, and also their Paralda unit. So I spent a couple days comparing these brand-new machines with my trusty stalwarts, my IQAir and Blueair.

First, The Boring Tech Stuff

It’s very important to know that my home’s machines did not have new filters, so true comparisons to these new Alen Air machines cannot be done. My Blueair’s filters were at least 4 months past prime, and my IQAir’s pre-filter was in the red zone. (Still, their data is also interesting). Anyway, I spent a few days wheeling around each machine in one of 4 rooms:

  • library, small bedroom and master bedroom: each around 10-12 square meters
  • front living room, itself 30 square meters and open into a large hallway and dining room, with no doors

I then measured each room’s pollution levels with a handheld Particlescan machine. This machine measures PM0.3 particles, which are much smaller than the PM2.5 which the US Embassy monitors. These tiny particles are what most scientists think are the causes of pollution-related lung and heart disease, as they easily get absorbed into the blood stream via the lungs.

I was “lucky” enough to be testing on days with the US Embassy readings in the high 200’s, so this was definitely a real-world challenge for any purifier.

The Real World Results

The good news is that both Alen Air purifiers did quite well, and indeed better, than last year’s tests of the IQAir and Blueair. For example, on average:

  • The A375 filtered out 94% of PM0.3 (96% at max setting) compared to the unfiltered part of my house (the hallway and back rooms); this was the best number I’ve had for any machine
  • The Paralda filtered out 80% (83% at max), also very good
  • My oldish-filtered IQAir filtered 76%
  • The older-filter Blueair filtered 66%

Another very positive point is that all purifiers did really well in bedrooms with doors closed. In fact, all four machines at maximum settings removed 95-99% of PM0.3! At quieter settings it was less awesome but still very good. I think this is powerful proof that air purifiers in bedrooms can dramatically reduce your pollution risk while you sleep — an issue especially crucial for infants and children.

In last year’s results from my previous apartment:

  • The IQAir filtered 74% on average, 84% at max setting
  • The Blueair 501 filtered 74% on average, 82% at max setting
  • In the small bedroom with closed doors, IQAir filtered 79%, blueair 73%
  • In the larger, open dining room, IQAir filtered 61%, Blueair 67%

Compared To Outdoor Air? Awesome

Don’t forget that the above numbers are comparing filtered rooms to a “control” room in a separate part of the house. So if you compare these above numbers to outdoor air, they perform even better. For all readings, I also stuck the Particlescan out of my 15th floor window and recorded this data.

On average, indoor air PM0.3 in my unfiltered hallway was 53% of outdoor air. I think that’s pretty good, and it’s a lot better than my previous apartment a couple years ago, which usually was around 70%. I think it shows how proper ventilation and window protection can help.

But what that also means is that these machines did even better than the numbers above. For example, if you’re comparing each room to outside air, the A375 got rid of 97% of anything bigger than PM0.3. Also:

  • Small rooms with closed doors were 95-99% cleaner than outdoor air
  • Open, large room was 29-39% cleaner than outdoor air

Don’t Forget Hunter, and Others

Last year I also wrote about a smaller and cheaper HEPA filter from Hunter, which in my readings routinely eliminated 50-70% of PM0.3 pollution even with the constant door opening in my 12-square meter office. At max speed with the door closed for a while, it got 91% of the pollution.

The Bottom Line

Clearly, with good filters, all these machines do really well in smaller rooms with doors, and I’m sure a bunch of other HEPA brands may also be ok. The larger rooms are always more difficult for all, but for the most important room — your bedroom — many HEPA models will probably be fine. Major differences between HEPA models include:

  • Price
  • Room size
  • Reputation
  • Noise
  • Replacement filter costs
  • Resale value
  • Other “features” (ozone, UV, remotes…)

Y’all can research all this other stuff; I’m just providing some real-world data to add to your decision mix. By the way, here is what Consumer Search says about the Paralda and the A375.

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70 thoughts on “Alen Air Purifiers Battle IQAir and Blueair”

  1. Thank you so much for the review. We hold our products to a high standard and we love to hear about a satisfied customer!

    By the way, could you change the title to “Alen”?

    Thank you again for your time and we appreciate you spreading the word about our products!

    -Alen Corp

    1. Hi, I think I remember hearing awhile back that Alen air purifiers don’t require the ongoing purchase of new filters–that you can just wash the filters and reuse them. Is that right? If so, where can we buy air purifiers from Alen Corp here in Beijing? Thanks! ~Aimee

  2. Hello Doc,
    Thanks very much for the information. Where can we get one super machine as you have to measure air quality?

    BTW, we began to use N95 masks for our family.


      1. Dear Dr.,

        did you borrow the scanner privately or commercially ? If the latter, I would be interested where, since the webpage of IQAir doesn’t mention a lending model.

        Also – I’m still looking for it on your great website: Do you have a take on air humidifiers and especially their possible negative side effects (germs) ?

        Thanks & best regards,

      2. I’ve always borrowed the machines that each company uses on their home visits. But the machine brand was always the same — ParticleScan Pro

        As for humidifiers, I’m a big fan of them in Beijing’s dry winter, but you indeed need to keep them superclean and germ-free. We always add some vinegar to our water tanks…

      3. Hydrogen Peroxide can also be added in low amounts to the cold mist (ultrasonic) type humidifiers. Bonus: helps beat lung infections especially bacterial and viral (also helps yeast, mycoplasma types of walking pneumonia)

    1. You can buy them for 2660rmb now. Search for ‘cw-hpc200a’ on Taobao. They count the particles at both PM0.3 and PM2.5 sizes. Then, you can just compare the ratio of the counts of inside/outside air.

  3. Hello,

    I have been reading a lot about air purifiers on your website recently. Before deciding on which brand/model to opt for, I wanted to ask if you heard about that product I stumbled upon.

    Philips AC4004 that seem to be a good option, at least on the paper.

    I cannot find any relevant review on the product performances and I was afraid that the price/features ratio was too good to be true.

    Any idea?

    Thank you

  4. You say: In last year’s results from my previous apartment:

    •The IQAir filtered 74% on average, 18% at max setting.

    Is “18%” correct??


    1. Whoops! Thanks for noticing that mistake! It should say “84% at max setting”…I just fixed it…

  5. When comparing to IQ the Alen price seems fair. Do you have the local reps contact details so we can get a home assessment from him?

  6. This detailed discussion of the filtering, monitoring process plus the comparisons with outdoor air and mentioning the health effects and indeed the EVEN SMALLER standard of 0.3 microns instead of the 2.5 and 10 are just HUGE!

    Really gives a much more thorough and visceral understanding of the problem….

    Am told that in 5 years China will adopt the 2.5 micron standard for monitoring rather than the 10 micron. Will 0.3 be the standard by then?

    Does anyone know of reliable (based on science) comparisons to cigarette smoking, e.g., if you live in Beijing, Shanghai or Chengdu it’s equivalent to smoking this many cigarettes a day?

    For most people, including me, still need more understanding of the MECHANISM by which air pollution inflicts damage is needed–there’s some great data out there in the medical literature re inflammatory markers and their response to filtering. Without that connection people ingnore pollution as another kind of simple dirt–not a big deal; but it is much more internal and damaging than that.

    And yet the Environmental Protection Agency (EPA) says that good CLINICAL studies are lacking to prove health benefits of filtering air, although the two authors on the topic that I’ve contacted use filtering themselves. I cannot believe that a well designed study in China, where the pollution levels are perhaps 5 times worse than America, could not show a benefit. Why isn’t someone doing such a clinical study?


    Steve Misch, M.D.
    Diplomat, American Board of Family Medicine
    Chief Physician, Chengdu Medical Center
    Parkway Health
    Chengdu Number 1 People’s Hospital
    18 Wang Xiang Bei Lu
    Chengdu, Sichuan China
    Tel: 86-28-8531-7899, Fax: 86-28-8531-2256

    1. Thanks for the detailed reply, Dr Misch. It’s always a pleasure to hear from another family doctor, especially from one in China! I think this process of learning about air pollution is very long but crucial. The mechanism of disease really is important; people do need to understand that pollution is a PRO-INFLAMMATORY DISEASE. The particles, when they hit the blood stream, release a series of pro-inflammatory molecules which are involved in many serious diseases including atherosclerosis, heart disease, cancers…many more. That’s why I always recommend people in China live as much as possible an ANTI-INFMLAMMATORY lifestyle. That literally means fruits and veggies and less red meats, as well as not smoking, and also consider antioxidant supplements…

    1. I’ve never heard of this brand, and I haven’t seen independent testing. Anyone have independent testing results?

  7. We have Alen air purifiers at our house, and I wanted to make an observation that doesn’t seem to be covered in the review, helpful as it is! We are happy with the units, and the effect on the air quality was immediate and perceptible. BUT, it must be noted, these are not what you would call quiet machines. The Alen flagship model has four speeds. Speeds 2,3,4 are on a par, in terms of noise, with a stove exhaust fan. Speed 1 is quiet, but I suspect it’s not terribly effective, either. When we have the devices on 1, I’ve noticed that the trademark Beijing smell (is that…sort of a coal-burning smell?) creeps back in. My guess is that you need to be 10 meters from the units, ideally, to ameliorate the sound issue. Not possible in my home. They’re loud enough that we have a problem with our guests simply switching the things off due to the annoyance factor.

    1. Yes, I did notice a sound issue with the 375…but at the 2 setting (not the max 4) I still found it effective. Yes, 1 is less useful but better than nothing overnight in a bedroom when it’s really bad out.

      All the machines are far too loud at max setting; we have the IQAir on 2 in bedroom and it still filters well. Our Blueair is really quiet except for the max setting.

  8. can i buy a A375UV or the blue air in united states for the lower retail price? Or will the voltage differences affect the perfomance of the machine?

    1. I’ve had some appliances from the US which worked ok here — only if you use the voltage converter. Many machines are already dual voltage, I’m not sure about these machines. Send their customer service an email and ask.

  9. Pingback: Hao Hao Report
    1. I don’t know. Philips is a good brand, but no true HEPA filter in any country is only 1000rmb…unless it’s a tiny desktop version…can you cut and paste the link?


      Richard Saint Cyr MD

    2. I don’t know. Philips is a good brand, but no true HEPA filter in any country is only 1000rmb…unless it’s a tiny desktop version…can you cut and paste the link?


      Richard Saint Cyr MD

      1. Hi Rich, nearly  a month now since i sent the link by email and here and still no answer. whats wrong?

      2. Hi again, sorry my response seems to be lost! Unfortunately I’m afraid it wasn’t very helpful for you anyway. I have no personal experience with Phillips and couldn’t find much online. I know they’re a good brand but I just don’t know. Did you access the official ratings on, or scan Those are always my first websites to check out.

      3. Hi again, sorry my response seems to be lost! Unfortunately I’m afraid it wasn’t very helpful for you anyway. I have no personal experience with Phillips and couldn’t find much online. I know they’re a good brand but I just don’t know. Did you access the official ratings on, or scan Those are always my first websites to check out.

      4. hi nope, those air purifiers seem to be for asia only. have u seen their spec-sheets? they claim to filter down to 0.3n thats way under pm 2.5 particle size. Have any chance to just look at their HK web side?
        CHeers Fel

    1. hi richard, i sent you the link multiple times here and via email. so far no idea if you got it also, i ve seen no posts from me lately which apparently didnt get approved. cheers fel

      1. Hey, sorry for the delay. Sorry but I still can’t offer any extra advice about those brands. I have no experience with them but it certainly is a reputable company, so I don’t think there’d be a problem. For any consumer product, I would check consumer websites at or, as well as user reviews on

  10. Thoughts on the panasonic f-pdf35c?  They’re only 700rmb on , and I just bought one, and it seems quite nice, but still, for example today, when I woke up I was sniffing a bit, and I checked the pm2.5 readings online, and found it’s a bit high, so I’m not entirely convinced this filter is removing the pollution very well?

    1. Panasonic does not use true HEPA filters in their air purifiers – they only claim to filter 97-99% of PM 2.5 (a true HEPA filter will filter down to PM 0.3 and smaller). Also, their claimed 5-year filter life should also set off alarms.

      Daikin is another popular brand that does not use true HEPA filters. However, they do use an intriguing photocatalyst technology in some of their models for the removal of formaldehyde and other VOCs.

    2. I tested a panasonic pdf-35c, using the cw-hpc200a, and it showed the pm0.3 count at the outlet port was only 10% of that in the room, but, it seems the flowrate is relatively slow, so the effect on my 60 square meter room is questionable, not much drop over 1 hour period.

      I’ve also bought an airoswiss aos 2061. This claims to be hepa, 99.97% yada yada. In fact, in my measurements, the pm0.3 at the outlet port was actually only dropped to 50% of ambient room pm0.3! On the other hand, I think the flowrate is perhaps higher than the pdf-35c, and combining this with the pdf-35c, at the same time, I get a 50% drop in room pm0.3, compared to outside, over a 1-2 hour period, in a 60 square meter room.

      Kind of looking around for something better really, but it seems it’s hard to get hold of precise measurements, on the internet, for any machine for:
      – flow rate
      – pm0.3 filter efficiency

      I’d kind of like to avoid buying one model of every filter, in order to find the best one 😛

      1. Thanks for the techy specs, I love it! I would certainly hope that both would work better, but 60 square meters is definitely a big space. Keep us posted over this horrible weekend, see how well they work!

  11. Beijing….Shanghai….China.. it doesn’t matter. Blueair works great for me and my family!!! I was tired of buying new machines every year. Oh, and the panasonic stinks by the way. Also had a Alen, but the thing was so loud it kept my dog up and barking and my kids always had trouble sleeping. I hear the IQAir is good too, but sorry, my expat package is not that big 🙂

  12. Just thought I’d leave our experience, for anyone interested. We have a 110sq meter home, on a second floor. We had three air filters: the Yadu KJF2801N, a Sanyo ABC-HP14 and a Philips AC4054. When we lived on the 7th floor and the air quality was averaging around 150 they were fine. We could both breathe far more comfortably, didn’t have the “Beijing hack” and our illnesses never degenerated into months’ long congestion and coughing as they had previously. (The Philips does put out ozone despite their claim that this model does not. The smell is unmistakable, and it would give us sore throats and headaches if used for long. However, it was excellent for smells on a short term basis. We did not use it for anything else.)

    However, two things happened in this new year. First, of course, has been the pollution levels. All this month it’s seemed like we’ve reached a new plateau-with 250 being the new “norm.” The second issue was the Yadu. When we got the delivery of the new filters, I noticed the HEPA type filter was different. The folds were larger and wider, and the number of them was much smaller compared to the old filter. The feel of the filter between your fingers was different. They came in the original Yadu box, and from the delivery man sent by Yadu’s main hotline. And, sure enough, either one or both of these factors meant that our filters were utterly overwhelmed this month. We both got sick, and our sickness worsened and eased directly in time with the pollution levels. At times we felt suffocated and could barely move off the couch, even when we closed off much of the apartment to give the filters as little work as possible.

    So we decided that after a month like this we can’t just hope that Beijing’s pollution levels will drop back down to their previous norms. Hopefully they will, but to simply assume so would be foolish. We have to assume that things are worse than they were a year ago, and respond accordingly. So we just purchased two Alen A375UV units. We looked into IQAir, but they were sold out till March 1st, and we weren’t willing to live like this any longer or go through the fireworks pollution without something better. Nearly every other higher quality (and higher cost) filter in the city was sold out. Alen was the only one we could find that had units that were ready to go and could be here in two days. Alen’s scores on all the independent sites that test purifiers in the USA were comparable to both IQ and Blueair. That and the experience that Dr. St. Cyr had and recorded here made us make the jump.

    We’ve been totally pleased with the Alen. Within an hour we were both breathing easier. The air smells clean and fresh, like being outside on a clear day back home. Our congestion has completely cleared up, we’ve slept much better and we’ve had more energy. We don’t have a particulate counter so can’t give numbers, but those effects are pretty good without a counter to confirm them.

    Two thoughts. The first is cost. If you’re planning to live in Beijing long term, do consider whether it really is worth it to try and get away with cheap air filters. If you live on a high floor, in an apartment that hasn’t been newly remodeled, with good windows and the air quality doesn’t go over 300 too much this year, you can probably get away with cheap. But if those things aren’t true, you may regret throwing away money on a succession of cheap models that don’t do the job when you really need them to. Yes, the Alen are costly, though not quite as costly as the IQ. We had to buy them with a credit card, and it will take time to fully pay off. But we decided that we could either spend those thousands on a trip back to America for 2 or 3 weeks of clean air and then come right back to the miasma of Beijing, or we could invest in having clean air all the time in our own home. If you look at it that way, it really changes your perspective on the cost.

    The second thought is noise. I have trouble understanding those who object to clean air because it’s too noisy to get it with a good air filter. I’m sorry, but this is Beijing and you just have to choose. Not to mention that I’m not sure why anyone wouldn’t love the white noise of a nice, loud air filter to drown out the cacophony of coughing, banging, clanking, flushing, slamming, constructing, broadcasting and playing that goes on in every Chinese apartment building; like the ubiquitous neighbor child who bangs out irritating piano pieces for 2 hours every evening on the other side of your wall. It’s really easy to get used to sleeping with a fan noise, and your kids might even sleep better and not be awakened by every little thing. Just a thought.

    1. Thanks for the insight and funny observations! And I didn’t know much about those other brands, so that’s helpful…yes, let’s hope that January was a fluke. I can’t wait to get outta here in a few days…
      Subject: [myhealthbeijing] Re: Alen Air Purifiers Battle IQAir and Blueair

    2. Thanks for the insight and funny observations! And I didn’t know much about those other brands, so that’s helpful…yes, let’s hope that January was a fluke. I can’t wait to get outta here in a few days…
      Subject: [myhealthbeijing] Re: Alen Air Purifiers Battle IQAir and Blueair

    3. Thanks for the insight and funny observations! And I didn’t know much about those other brands, so that’s helpful…yes, let’s hope that January was a fluke. I can’t wait to get outta here in a few days…
      Subject: [myhealthbeijing] Re: Alen Air Purifiers Battle IQAir and Blueair

  13. Does anyone know about using central heating forced air systems and air purifiers? Our apartment has those hotel type warm air ducts blowing air into each room from near the ceiling (ultimately provided to the whole compound from a large central heating unit). If that is outside air blowing into the room then it may undo all the good work of the purifiers. Anyone understand the mechanics of this and any suggestions?

  14. does anyone has a Air-O-Swiss AOS 2071? What are your feedback on the product? from the spec it feels like it a machine which can combine both humidifier and air cleaner (2 HEPA filters). That sounds perfect for Beijing. I didn’t find much reviews online though.

    1. I do, but note that their filters are only H8, they’re at the same level as the ‘pre’-filter on an IQAir, which I’m thinking of upgrading to next, once I’ve saved up a bit 🙁

  15. One thing that interests me about the IQAir is that they have various inflow/outflow solutions that most of the home air cleaner cannot easily support (but of course, as we all know form MacGyver, there is nothing you cannot do with some duct tape)

    For extreme problem cases like winter Beijing, I would assume that there is really now way you can stop the polution issue unless you create a positive air pressure in the room?

  16. Hi,
    I am by the way a big fan of your site, but was wondering if you could tell me why (or how it is possible that) your IQAir gives you a 76% filtration efficiency? That sounds to me that the unit is not properly closed, the filter is punctured or there is something else wrong with the way you measured the filtration efficiency or how you use the unit in the first place.

    I have been using air purifiers in the most polluted environments for more then 10 years. I have used laser particle scanners and tested more or less every unit that has come my way during that time. I have never seen an IQAir with a 76% filtration efficiency, no matter how old the filter is (the basic physics of it simply does not make sense).

    Have you have seen the video where a person is exposed to very high levels of particle pollution ( You would not be able to do that with a Blueair unit or any other unit that gives you a <76% filtration efficiency.

    In mechanical filtration the filtration efficiency increases not decreases. So I wonder if you can tell me a bit more of how exactly you measure the units filtration efficiency?

    Thank you.

    1. Hi Peter, I think you are mixing up technical “filtration efficiency” with real room data. I am measuring the room’s PM2.5 levels, sometimes comparing to another room and sometimes to the outdoor air (depends on which article). Sure, the IQAir filtration is basically 100% when you stick the particle monitor against the IQAir’s filtered air — amazing results. But I am doing real world testing, and CADR and inflow of pollution and room size all come into play. I’ve done three extensive tests of multiple air filters, including another one I am currently editing — and no machine ever did better than 85% total “real world” room efficiency when averaged out. In small rooms with doors closed, I can easily get 99% room efficiency overnight with many models.

      You bring up an excellent point — just because a filter is rated 99% or HEPA doesn’t mean it’s going to filter 99% of your room air after turning it on. It totally depends on room size, CADR, the speed you choose, etc etc…a filter rated in the 80’s can be just as effective in the real world as a 99% rated filter if the flow rate and CADR compensates for that…

  17. Hi,
    Quick question, can/should you run a air purifier and humidifier at the same time in the same room?
    I recently purchased a purifier and now the air is drying out for winter and I’m worried that the moister from a humidifier could damage the air purifier…


    1. I’ve never heard of such a problem. We definitely use both. Beijing’s air is super dry in the winter, you need to keep indoor humidity levels 30-50%

    2. You only need to be careful about moisture if your purifier uses zeolite and/or potassium permanganate (for the removal of VOCs). The former absorbs moisture whereas the latter will actually have a chemical reaction with water.

  18. Hi,

    Have you heard of Healthway Air Purifier (sometimes called Clean Station). They use technology called DFS, rather than HEPA filter system. They claim this is the world’s most powerful air purification system. Can this brand be trusted?


    1. Sorry, never heard of it … what does say about them? I haven’t heard of any true alternative to HEPA…and what’s the cost?

  19. I m quite surprised about what you have to say about humidifiers if you really have done your tests.. I recently acquired a top of the line humidifier to go along with the IQ air 250 in the living room and the Phillips AC4083 in the bedroom…
    The Philips purifier got a color meter that tells you how good or bad the air is.. As soon as I switched on my Air-o-Swiss humidifier with brand new filters the meter goes red within seconds. So I started to dig a little deeper to find many articles that says if you are using tap water the indoor air can contains up to 28 times the 2.5pm and 10pm particles than outside air!
    So in other word you got a machine that send small particules and another one that removes them ?!

    Unless you have a reverse osmosis water purifier you better not use humidifier!!

    1. I think you’re missing a major point here: Water in all forms, from the single molecule to a drop of water, is completely harmless to us — it is, of course, the exact opposite, the most necessary molecule every organism needs to live. So there is completely no worry about water as a “particulate” you breathe in. You should focus your anger and concern on your air purifier’s cheap particle sensors, which clearly can’t tell the difference between water vapor and truly harmful chemicals… This is one of the big reasons why most people don’t find auto-sensors very reliable or useful…

  20. Yes, pure water… If every water is so good for you then why don’t you drink a good glass of Beijing tap water?

    And I typed with my phone so I made a a typo on particules .. What kind of arrogant OP are you?

    Here is an article from the very same website:

    And here is one of the first page you come accross if you google:

    I’m not sure why you think I’m angry, I was just trying to contribute to the topic?!

    1. I’m sorry but I wasn’t poking fun of you at all when I said particulate, I didn’t even realize you misspelled. I said particulate in quotes to emphasize that everyone thinks of “particulate matter”, PM these days, it’s all the buzzword. And I didn’t want you putting water in that category; water is not considered an air pollutant, so it’s just not part of PM consideration.

      Your PDF is quite interesting! Most of the elements they found in the indoor air were just raw elements like calcium, but if water is polluted with heavy metals like lead, then I suppose that could be a potential problem. It’s an interesting idea, but I’d certainly like to hear from experts about all of this, as I’ve never heard any official statements against humidifiers as an air pollution problem. Perhaps our readers can help? Regarding humidifiers, I now use filtered Aquasana water in my ultrasonic humidifiers — but may switch totally to reverse osmosis to eliminate the calcium deposits.

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