How to Choose an Air Filter in China

air filterOne of the most frequent questions I get asked is “What kind of air filter should I get?”  This is great to hear because it means that people recognize the need for clean air and are trying to do something about it!  Also, in China, the level of air particulates indoor is quite high and we regularly see clients test at levels that are as high as 15x that of the EPA annual standard (15 micrograms/ cu. meter of air).  There are multiple solutions to high particulates, but oftentimes, clients want to achieve cleaner air without a lot of change in their daily habits.  (ie. washing your cat). Or, if you close your windows to the outside air, you can cut down your particulates but at the cost of less ventilation, which can generate stuffier air and higher levels of other indoor pollutants. Air filters (sometimes called air purifiers) are a good way to both make a big dent in particulate levels, and some can also reduce odors or toxic gases. For options we have, please check our online store.

usb laser purifier

Uh, no.

Unfortunately,  it’s pretty confusing, especially when you are trying to do your homework and have each brand salesguy telling you a different thing.  There are also a lot of different technologies out there, many of them proprietary and unfortunately, gimmicky.

Since I test air for a living, I’ve had the chance to evaluate what’s out there, play with the units, and spend time with the product reps.  Today, I had a call with a client who is very conscientious about her health and is doing all the right things, but still had a high particulate (PM2.5) count and wanted to know what she could do.  There are a few general points I shared with her that I’ve replicated here:

1. Get the filter that is right for your situation or problem. For instance, someone who has recently renovated and has high levels of formaldehyde needs a different purifier (something with a gas filter, usually activated carbon) than someone who has allergies or asthma (HEPA filter capable of filtering the smaller particles likely to trigger allergic reactions) than someone who has a compromised immune system (special type of HEPA filter capable of ultrafine filtration plus UV-light to kill bacteria or viruses). The big differences are particulates, odor/gas removal, and ability to kill microbes. Like everything else in life, trying to get one that does everything well will either cost you a lot or sacrifice performance somewhere else. Spending some money to test your air first can help you identify what to get and save you from overspending on a filter you may not need.  Here’s a primer on what are the most common pollutants in Shanghai, their sources, and health effects.

2. Look for HEPA (high efficiency particulate absorbing) filters. It’s a dirty secret, but all true HEPA filters will filter 99%+ of particles sized 0.3 microns or larger. A filter cannot be called HEPA unless it meets this industry standard. For reference, a human hair is about 40 microns thick and your body (if healthy) does a pretty good job of naturally removing particles 10 microns or larger. The smaller, the worse it is for you because the smallest particles bypass the body’s nasal hairs and mucous (yes, the Beijing hack does serve a purpose!) and penetrates deep into the upper lungs and into the bloodstream.  There’s a pretty complete guide for particle  sizes, but strangely, they don’t list one of the most common allergens  – can and dog dander.  (for the record, around 2 microns) Avoid things that sounds like “HEPA-like” or “partial HEPA”. “True” HEPA is ok.

Alen Air Paralda

The finer the filtration, the better, right? Nope. The finer the filter, the harder the machine must work to push the air through the filter — the only way it can do this is to either have a stronger motor (louder) or wear out the filter faster. Just get enough for what you need and don’t get swayed by one manufacturer that says they can filter 99.97% vs. their competitor who “only” filters 99.3%!

3. That said, all HEPA machines are not built the same. The capability to circulate the air is very important. The larger the room or living space you’re trying to purify, the more important this is. Generally, this is where the larger, more expensive machines shine. IQ Air, Blueair, Alen, are the biggies in Shanghai and all of them do a good job of ensuring that all of the air in the dimensions their machines are rated for are clean. Ask to see the manual to understand the number of air changes they can do every hour as a common metric.

blueair air filter
Blueair purifiers can provide either particulate or gas filtration, depending on filter you put in

However, this is only useful if you understand what efficiency the air is being cleaned at. If you only need to clean a single room (ie bedroom when sleeping), you can do well on a limited budget with a small HEPA purifier. Or, you can drag it around with you wherever you go on a long extension cord (not a joke — one of our clients does this).

4.  Avoid purifiers that produce ozone.  Ozone is a gas that is extremely reactive and forms byproduct gases on contact with organic material.  In the atmosphere,  it protects us from UV and in water, it is used to disinfect.  But, if you breathe it in, it is very damaging to the body, causing coughs, chest discomfort and eye, nose, and throat irritation.  It can also aggravate asthma by increasing sensitivity to allergens and cause long-term scarring of lung tissue.  There is a 30% higher incidence of lung disease in cities with high ozone.  A few machines produce ozone to attract particles which drop to a collection tray or worse, emit ozone.  Remember the Sharper Image’s Ionic Breeze machine?  Shows you what millions in marketing dollars can do when an air purifier creates more unhealthy air than you had to begin with.  Most retailers and manufacturers avoid ozone like the kiss of death, but this is China and you never know, so check the fine print.

5. Noise. You’ll be trying to sleep while it’s running. Manufacturers have a decibel rating, but this is not very useful — I’ve seen some of Blueair’s machines’ rating to be inexplicably high when the sound is actually much lower in practice. Go and test out the machines before you buy on all speeds. Better yet, listen to it in someone’s house instead of a noisy salesroom floor.

6. Cost of filter replacement. This is a biggie. Think total cost of ownership over time for the filter you need. Alen and Blueair are quite similar, at about 500-700rmb / 6 months. Filters with gas removal capability usually cost more because they add carbon to the mix.  IQ Air is about twice that. There are some interesting models by Sharp (Plasmacluster) that can be washed (including the carbon odor/gas filter), which means you actually don’t need to replace the filter for 5 years. However, I haven’t seen how efficient these are over time.  Models that have a precleaner that can be vacuumed may extend the life of your HEPA filter.  Most importantly, change your filters according to the recommended guidelines!  A 1000rmb HEPA Yadu purifier with a new filter will clean your air better than a 15000rmb IQ Air Health Pro Plus with an old filter, hands down.

7. Why not just buy a unit from the US (usually cheaper there than in Europe) and bring it here? Assuming you don’t want to use up that luggage allowance bringing over salami, nice hard cheeses, or 20 iPads to sell here, there is a matter of voltage. US machines will be 110V, requiring a transformer here and if you run the machine 24/7, the transformer will waste a lot of energy being constantly on. Even if that didn’t bother you, there’s a reason that the manufacturers don’t recommend this. The cycle is different. US are on 60 cycles, China is on 50. Transformers change the voltage but not cycles, meaning that the motors run at a different speed than designed, causing all kinds of mechanical weirdness and potentially different filtration results. I am not sure if this voids the warranty, but it wouldn’t surprise me. Just don’t do it.

8. Don’t undervalue after sales service. The three brands I mentioned before all have local product experts who will support you, answer your questions, differentiate between models, and continue to provide filters and warranty service after the sale. They also will be able to answer your questions halfway intelligently as opposed to the brand sales clowns in Gome or Suning who will look at you like you’ve got a pecker growing out your head if you start asking these questions. When I first came to China (before getting into the testing industry) I bought a big Yadu and Malata, another local brand. A year later, when it was time (overdue actually) to replace the filter, the retailer no longer carried the model at all, and when I got a factory number from them, the factory didn’t have the filters anymore. I ended up with an expensive paperweight (actually houseplant stand). Don’t be penny wise, pound foolish.

Bottom line, air filters are good (not always the only answer for indoor air problems though), but you should figure out what problem you have before you buy one to avoid wasting money. Don’t be swayed by your buddies who probably don’t have experience with anything other than their single machine. Get the right purifier for the needs you have and think about total cost of ownership (including your time) over a few years, not just the initial purchase.

Feel free to ask any other questions about this or filtration technologies here — later on, I’ll touch on some of the other technologies out there besides HEPA filtration and gas adsorbtion with carbon-based compounds, like photocatalytic oxidization (PCO), ultraviolet (UV) light, and ionization.

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How to Choose an Air Filter in China

  1. Anonymous says:

    goz goz

  2. BW says:

    “(IQ Air suitable for a 60m2 taking up floorspace in a tiny 12m2 nursery)”. IQAir’s HealthPro 250 covers about 40 to 45m2 on maximum speed. On medium speeds, expect it to cover less than half of that, especially if the room has high ceilings. On the lowest speeds, it could just be perfect for a 12m2 nursery.

    Formaldehyde is taken care of by carbon in most of these machines. Formaldehyde reduction rates therefore reflect overall chemical reduction rates. Not including effective carbon in air filters machines is a big mistake, regardless of whether formaldehyde itself is present in the room.

  3. Jane says:

    I have been comparing few air purifiers brands (Blueair, Philips, Plasma cluster, Electrolux)
    I’m thinking of buying the Electrolux Z9123 (2778 RMB).
    But, from a survey ( it looks that the formaldehyde efficiency removal is very low (16%)
    compared to other brands, such as Blue Air or Sharp.
    I live in Beijing in an old building just near the 3rd ring. Any advice for the choice of an air purifier?
    Another question: is it ok to put humidifier + air purifier from 2 different brands in the same room?
    Thank you!

    *** Forbidden. Need manually approve. Request number ab96992872dbae5054b7db4e1cb49638. Antispam service ***

    • Louie Cheng says:

      Jane, we always advise testing as a way to know what filter to get. All too frequently, we see either overkill (IQ Air suitable for a 60m2 taking up floorspace in a tiny 12m2 nursery) or the wrong thing (HEPA-only filters in an environment that has a chemical problem).

      There is no way to know what is suitable for you without knowing more about your individual case and taking a look. If you don’t have a formaldehyde problem, why would you worry about formalehyde reduction rates? Also, a specific model is going to mean more than a brand. A Blueair 503 has about 4x the carbon as a Blueair 203 even though they’re the same brand.

  4. Peter says:

    Hi, Interesting article;
    “The cycle is different. US are on 60 cycles, China is on 50. Transformers change the voltage but not cycles, meaning that the motors run at a different speed than designed, causing all kinds of mechanical weirdness and potentially different filtration results.”
    I see that the iQair GC in the US is rated as a 120v 50/60Hz machine. Assuming that a 220V step-down Converter (Incl regulator) is used, I would’ve thought that the US model would work fine in China as the machine is spec’ed as 50/60Hz?
    I thought (could be wrong) the fans are controlled by Direct Current on the majority of purifiers, therefore the Hz does not influence the speed as they are not clocked off the mains cycle.

  5. HEPA Air purifier review says:

    Your post was wonderful! I have one product Mammoth Air Purifier. You never know… You have to do a certain amount of look up and determine which web-site could give you the cost you are looking all by yourself.
    Come here and check out whether or not HEPA Air Purifier is really cheap or not. HEPA Air purifier review

  6. Gabby says:

    Hi, I need an air purifier. I went to the doctor the other day for seems like the development of asthma. I don’t have it yet, but I’m hoping to try and prevent it from further developing. I will only live in Shanghai until May so I don’t want to invest hugely in this… just something that can help until I finish. Do you have any recommendations for someone like me? :) Any info is appreciated, loved your article.

    • Louie Cheng says:

      Hi Gabby, what most people do in your shoes is to purchase a quality air purifier and then sell it used when you leave. If you find a second-hand one, be sure to change out the filters, since you don’t know what was in there before. If it’s a carbon filter and is full (cannot adsorb any more), chemicals can actually leach out and increase the chemical level in the air. We’ve seen this happen. Be sure to add in the costs of a new filter change to the second-hand price.

      One final option is to lease. We offer 3 month – 2 year leases on machines, including delivery and pickup and all maintenance.

  7. Marina says:

    Your post was wonderful! Thanks a lot for sharing it with us…
    We are all a little bit worried about living in air polluted areas and are looking for solutions to get a little bit better :)
    I’d like to have my indoor air tested as well but I live in Suzhou: is it possible? Could you please contact me?
    And also suggest me your best solution for us?
    Thanks a lot in advance

    • Louie Cheng says:

      Hi Marina,

      Sorry for the delayed response — it’s been a very busy week!

      Yes, we can and have done Suzhou before. The testing price would be the same but there would be a travel surcharge for the time and added expense. Ideally, if you could get another friend, the charge could be reduced. Please contact us at or at the SH office: 021-3469-2269.

  8. tiago dantas says:

    how can i test the air inside my house? i live in shanghai and my wife wants to buy the IQ air and i do not know which model is the right one for our house so who do you recommend that provides these type of service (air testing and recommend the best air purifier according to our needs )

    • Louie Cheng says:

      Hi — that’s exactly what PureLiving does. We’ll have someone get back to you soon to propose the right testing.

  9. Tim Dearman says:

    While an overview of the various approaches is of value, is there ANYWHERE available a listing of various brands and models of filters available in China, complete with a matrix of design features and meaningful specs and possibly MSRP prices so that one can compare features, estimated consumable costs and total price and an estimated operational cost associated with them?

    Understanding the need and use of filters is not difficult. But learning what is and is not available in China is near impossible.

    Thank you.

    • Louie Cheng says:

      Agree that getting info on filters is confusing. This posting was to suggest the most relevant criteria for which people can go shopping for filters. We do offer a cross-brand and cross-model comparison for our clients as an advisory service and recommend what specifically is most suitable during the post-testing debrief.

      Since this is a benefit for our clients, we don’t post it publicly, but if you’d like it, please drop us a request at and we’ll send you a copy.

  10. Thank you for the sensible critique. Me and my neighbor were just preparing to do a little research on this. We got a grab a book from our area library but I think I learned more from this post. I am very glad to see such excellent information being shared freely out there.

  11. Excellent review, Louie! I’ll be mentioning this post on my blog as well. Keep it up! And the company idea is excellent; perhaps you can set up in Beijing as well?

    • Admin says:

      Dr. St Cyr,
      Welcome! Would be great to have a resource like your site here in Shanghai as well. Do you have a counterpart down here? Given the recent state of particulate air pollution in Beijing, it definitely would make sense to set up shop there, but for now, we’ve got our hands full with Shanghai. Feel free to ask any questions here about Beijing or direct your patients or site visitors to ask here.



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