UPDATE, MARCH 15: this project is now on hold (details here)
Wow, that wasn’t very fun, was it? We just finished a miserable six days of AQI over 300. But it certainly was the perfect backdrop to my new campaign to test air pollution masks, and I’ve been busy all week with interviews with CBS News, the LA Times, Wall Street Journal, South China Morning Post, and Quartz.
Now it’s almost a week into my fundraising campaign and I’d like to give everyone a quick update:
- First, this is my personal campaign, a worried father’s tilting-at-windmills quixotic (obsessive?) quest to get evidence-based data on which pollution masks can help my Alex, myself, my patients and their children — everyone, everywhere who lives in polluted environments. This has nothing to do with my hospital, and I have no sponsorship or official backings from them or anyone else, including mask companies.
- No mask company has any control over what I will test or publish. Good results, flunking results — everything will be published here on my blog.
- I make no money from this project. Any extra money would go directly to the wonderful Roundabout charity in Shunyi. Any extra masks also will go to them. I wanted to also donate the tested masks, but apparently they are destroyed from the test due to a big hole punched in them, so we have to throw them away afterwards.
- I understand that people may be concerned about a private donation and not knowing where their money is going. To help reassure people, and for 100% full disclosure, everyone can “follow the money” at my online Excel spreadsheet here http://1drv.ms/1jNoq9k
- A few companies have already nicely promised to donate masks for testing. I hope others as well can help.
- As of today, I have raised over $1,000 in funds from the crowdfunding website rally.org as well as from Alipay donations (plus the donated masks). That’s a great start — but I still have a long way to go in fundraising as I need almost $10,000 to test all the masks I’d like to test.
- The fit-testing company, FROST, in sunny California has nicely offered a discounted price of $25 per mask test. I plan to test over 180 masks, so 25 x180 = $4,500 just for testing.
- Rally.org is one of the many crowdfunding websites, a revolutionary advance for anyone to raise money for projects. But this convenience comes at a cost, and Rally.org takes 5.75% of transactions. That’s actually lower than the other major crowdfunding sites, which is why I chose them. If you want your money to be even more efficient, you could use Alipay or Paypal directly to me (email me below for instructions).
I know that many of you are excited about this project and would love to see this data — but there won’t be any data if I can’t raise the funds. To contribute and show support, please click here to go to Rally.org and contribute via credit card (cards are accepted from all countries). If you want to use Alipay 支付宝, please transfer to my account under my email account at . Anyone with questions about this campaign can also contact me at the same email address.
Here’s today’s CBS This Morning video:
What’s the hottest gift this Chinese new year? Perhaps instead of moon cakes and red envelopes, you could give “the gift that keeps on giving”: an indoor air purifier. They certainly are all the rage in China since last year, with skyrocketing sales and sold-out inventories after the trio of highly publicized airpocalyptic crises. I think this is a good turn of events: plenty of independent testing, including mine, has documented that a good air purifier can dramatically improve your indoor PM2.5 by 80% or more. But is there any good data that proves that this actually makes you healthier? It seems logical, of course, that decreasing exposure to pollution would decrease harmful health effects. But medical history is filled with tales of common sense and tradition that later turn out to be worthless or harmful — like bloodletting, or the more modern tradition of multivitamins. A big percentage of people reading this article take a daily multivitamin, assuming it’s “healthier” to do so, but the best evidence shows they are worthless, and possibly harmful. Could air purifiers be the same?
In theory and in testing, a good purifier should improve a room’s pollution levels more than 80%; this 80% reduction is also what the private Association of Home Appliance Manufacturers (AHAM) uses in their clean air delivery rate (CADR) tests, which are widely cited in comparison charts of air purifiers. So let’s say you’ve installed a top-of-the-line purifier in your living room, feeling quite safe and cozy. But how much of your time is actually in that filtered room? Or maybe the purifier is too small for that room size, or the filters are old, or the fan speed is too low, or the windows are open? Even this commonly cited CADR test is just a lab test for only 20 minutes — what about in the real world? I want to take this conversation to the next level, seeking out proof that your health will improve when using these machines. I want to be able to tell my patients and readers that there are published research studies which followed people over many months or even years, compared them to a control group not using air purifiers, and measured their health to see if there was any improvement in heart and lung disease, cancers and death rates. Are there any such studies?
I searched the Pubmed scientific database to find the best studies, and I was disappointed but not surprised to find very little strong data. A properly designed research project like this would be very difficult and expensive. But there are a few attempts, especially studies looking at using HEPA filters to help children with asthma. One was a systematic review published in 2002, which found that air filters helped to improve asthma symptoms — but the effect was small, and there was wide variation between studies which made conclusive assessments difficult. A more recent, very well designed study published in Pediatrics in 2011 followed two hundred children with asthma who also were exposed to secondhand smoke at home, and gave half of the kids a true HEPA purifier and the other half a fake purifier for their bedrooms. After a year, the HEPA group of children had less doctor visits for asthma flares, which possibly — but not conclusively — could be due to the 25% decrease in PM2.5 in their homes.
Other studies have focused on allergies, including an interesting study from 2008 which assessed children with documented pet allergies, following them over a year and recording lung function and blood markers. After a year, those who used HEPA air purifiers showed no clear difference in lung function, use of allergy medicines, or blood markers of allergies. Another study back in 1990 was a bit more impressive, showing not only a 70% reduction in indoor PM0.3 but also improved patient symptoms of allergies.
All of these hint at health benefits, but they still dance around the edges of what I want to know for us in China and the developing world. In the USA, most of the air purifier marketing and testing focuses on allergies and asthma. But here in the developing countries, the air pollution is much more severe and thus the health risks are far more serious. We are worried about pollution’s long-term risks of death, heart and lung disease and cancer. These studies I just mentioned still aren’t answering that deeper question: can long-term use of indoor air purifiers prevent death, heart and lung disease, and cancer?
The best study I found was published in January 2013 in Indoor Air. It was very well designed for this complicated type of study, being a randomized double-blind crossover study of 20 homes over three weeks, using an air purifier or a placebo purifier. Their main goal in this remote First Nations community in Canada was to assess whether air purifiers could improve cardiorespiratory health. As their abstract says,
“…each home received an electrostatic air filter and a placebo filter for 1 week in random order, and lung function, blood pressure, and endothelial function measures were collected at the beginning and end of each week… On average, air filter use was associated with a 217-ml increase in forced expiratory volume in 1 second, a 7.9-mm Hg decrease in systolic blood pressure, and a 4.5-mm Hg decrease in diastolic blood pressure. Consistent inverse associations were also observed between indoor PM2.5 and lung function. In general, our findings suggest that reducing indoor PM2.5 may contribute to improved lung function in First Nations communities.”
This same Canadian research team had earlierpublished a similar study, testing 45 non-smokers for 7 days in 20 homes that used wood stoves, comparing health effects with or without HEPA purifiers. The people using the filters showed improved endothelial function and biomarkers of inflammation such as CRP. As most pollution researchers now see pollution as a pro-inflammatory disease, testing for such biomarkers could indeed be an accurate surrogate for later health problems. This approach is also being used in studies of air pollution masks, which I recently reviewed.
My take from these studies? Firstly, they all confirm what we already know: air purifiers can reduce the levels of indoor PM2.5, but with a wide range of effectiveness. Secondly are the more important results looking at health markers. I think the most encouraging finding was the First Nation study showing improvement in lung function, even in such a short amount of time (less than a month). Their data was a bit less convincing on blood pressure improvements, but perhaps a larger study would help confirm their initial findings of a slight improvement.
None of these studies are slam-dunk proof for me, but I honestly don’t know whether we ever will get many more well designed studies like these, unless governmental researchers or Gates-type philanthropists fund them. But until better studies come along, we must rely on what we do know:
- Air pollution contains many chemicals, but PM2.5 is considered to be the most harmful to health.
- There is no such thing as a “safe” level of PM2.5. Lower is always better.
- Worsening PM2.5 causes deaths from all causes, especially heart and lung diseases and cancers. Many studies have shown this, including this 2013 meta-analysis of the population in China.
- On the brighter side, long-term improvements in PM2.5 do help to decrease mortality. The best study was a huge epidemiological analysis of entire populations in American cities as the air improved from the 1970’s to 1990’s. Lifespans improved for everyone, for a multitude of reasons, and they estimate that 15% of the improved life expectancy was due to cleaner air.
- Shorter studies have also shown improvements in health from better outdoor air pollution. The best designed study I’ve seen on this happened right here in Beijing, during the 2008 Olympics. A team of researchers followed 125 healthy young doctors before, during and after the Olympics, and found improved blood pressure, heart rate and other biomarkers of inflammation during those lovely days of improved air pollution. Another encouraging study followed pregnant women and their babies in Tongliang, China both before and after a heavily polluting coal-fired power plant was forced to shut down in 2004, and found improved neurodevelopmental scores in newborns at age 2 years.
Is all of this enough to convince you to use an indoor purifier? For me, I was already convinced years ago — it’s not just common sense, it actually makes biochemical sense and also perfectly fits with the precautionary principle: “When an activity raises threats of harm to the environment or human health, precautionary measures should be taken even if some cause and effect relationships are not fully established scientifically.”
Last January we had the airpocalypse, and this January — hell hath frozen over. Because a bright-eyed Fulbright scholar and his disciples are spreading across China, preaching in their revival tents to swooning crowds that “you — yes, YOU, ma’am, in the corner!” (rising applause) “Yes, I swear to you right now that you can make your own air purifier for under 200 RMB — and get the same results as your fancy-schmancy, Perrier-sipping import! Can I hear a yee-haw!” (wild clapping).
I refer to Thomas Talhelm’s evangelistic, data-filled blog and his company spinoff, Smart Air Filters, offering frequent DIY workshops on just this subject, as well as selling their own two models. And yes, the cheaper one is really only 200 RMB. Crazy, no? Like a fox, maybe. Because Thomas’ scrupulous data, far geekier than anything I’ve written (that’s a compliment), does indeed show quite impressive PM2.5 reduction with these machines, even when directly compared to some famous models we all know about.
Thomas actually was inspired to do his own testing from all of my own tests and blog posts, and we’ve been emailing back and forth since last summer, comparing notes. As I mentioned last week in my Philips review, I’m quite a fan of his goal to find affordable protection for the masses against indoor air pollution. And his message has spread quickly, with many news groups covering the story. Many of my readers have asked me to review his machines, and I recently got to test both his Original and Cannon. So how did they do? Is he a prophet or a charlatan?
Let’s cut to the chase: a true HEPA filter and a strong fan indeed are all you need to eliminate bad particles in the air. Almost every top air purifier machine out there, no matter how fancy, is still built around those two pieces: a HEPA filter rated to eliminate 99% of particles larger than PM0.3, and a fan blowing air through it at a proper flow rate. No other features really matter as much as this, at least here in China. If you have a car, a HEPA filter can go into your exhaust system and clean your air; if your home or office has an HVAC system, installing a top-rated HEPA filter is incredibly effective, and much cheaper than a floor machine.
So yes, it makes perfect sense that a do-it-yourself combo could work — and it does. I tested the smaller Original model in my three small rooms, 10-13 square meters in size, overnight with the doors closed. And this little guy did about as well as any other machine I’ve tested: PM1 levels were 91% lower than the outdoor air, and PM5 levels were 95% better. This was on its lowest speed setting, which was tolerably loud but certainly noisier than my usual Blueair settings at night. In my most recent testing of Blueair, IQAir and Airgle, I got bedroom results of 88-90%. For small rooms, this little HEPA filter was at least as efficient as all of the big boys.
Thomas tests his machines a bit differently than I do, comparing them to the same room before and after, and he also measures PM0.5 and 2.5, whereas my Dylos machine measures PM1 and 5. He also mostly tests on highest fan speed, which I find impractical and too noisy for a real world scenario. But even with these differences, we still got about the same results: effectiveness always at least in the high 80%, which also at the very least was a strong match to the bigger machines — sometimes better.
So our data does match, and again why wouldn’t it? He’s using a real HEPA filter and a fan with a flow rate that works. I think their smaller Original model is especially a reasonable option for students and people with limited income to use in their bedrooms. It certainly is far, far better than having nothing at all, when the AQI outside is crazy bad.
His newer machine, the 450 RMB Cannon, was designed for bigger rooms, and I think that also could work well in theory, since it’s the same HEPA filter on a stronger fan. I wish I could share hard data with you, but honestly I didn’t get a lot of data points on this machine, mostly because it was just so darn noisy that I didn’t want to test it any more in my living room. Even at the lowest setting overnight, it was much louder than normal background decibels from my current IQAirs. For me at least, that’s a non-starter as an option. Thomas openly admits that the Cannon is a bit loud, but it still is effective even on low settings (see the graphic to the right).
But let’s not get bogged down in the details of these two models. These are early, first generation attempts, and besides, it’s distracting from his and my main message: everyone everywhere should always try to limit their exposure to pollution, and a DIY HEPA filter and fan combo are a heck of a lot better than nothing at all.
I assume the PR teams at the famous air purifier headquarters are now champing at the bit to correct me, aghast that I would gloss over their superior technology. And of course that’s partly true, as some top end filters do indeed claim to filter down to PM0.003, a hundred times smaller than a normal HEPA. Not to mention the other filters for VOCs and other chemicals besides PM. And maybe that does matter in a place as polluted as China — but I haven’t seen any data or medical resource claiming any specific advantage in targeting those ultrafine particles. Perhaps in the next couple years, with better research, we may learn that spending that extra $$ on the top end models may prove more beneficial to your health.
Until then, I say to the hundreds of thousands of people who’ve bought air purifiers: keep up the good work. But for the hundreds of millions of unprotected people across the developing world, anxiously awaiting the next inevitable airpocalypse — go get a HEPA filter and stick it to a fan. And buy yourself a particle monitor, test your machine, and blog about it. Viva la consumer revolution!
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.
I’ve blogged a lot about testing my air purifiers at home, a quartet of machines (three IQAirs and one Blueair) working in symphonic harmony to create indoor air 80% cleaner than the outside air pollution — 24 hours a day, every day. I find this 80% to be very reassuring, especially for my newborn son, who will be spending almost 100% of the first years of his life inside our home. Air purifiers in China are a no-brainer, must-have item! I would be even more cheerful if one more criteria could be improved — the cost.
Each time I pay for replacement filters, I get really ticked off that I’m paying so much money — and so much more than I would than if I lived in the USA or Europe, ordering exactly the same filter. It’s simply infuriating that a replacement filter in China could cost more than an entirely new machine in America! In the respected Consumer Reports list of top air purifiers, the highest rated machine is only 2,118 RMB (~350 USD, the Whirlpool APS 1030K). Even the Chinese press has started to cover the extortionate prices of some air purifiers, especially the replacement filters.
I actually feel partly responsible for this, as many thousands of readers have bought machines based on my recommendations. Here in our expat bubble world, sheltered underneath our shiny pollution domes, we all keep self-promoting the same heavily advertised imported brands, creating a self-reinforcing illusion of brand superiority. Meanwhile, the other 99% of people in China couldn’t possibly afford almost any machine I’ve recommended. So while I appreciate my current machines, and while they truly are highly rated from many independent sources, they are far from the only viable options out there — and definitely not the best value for anyone with limited income.
I can’t say I’ve found the perfect solution quite yet — perhaps the team at Smart Air Filters could help fill that gap — but I may have finally found a decent value. It’s the Philips range of air purifiers, especially the AC4072, which I recently gave to my in-laws as a Christmas gift (only in China would that be a hot gift!). I chose this because it ranked very well on the test results last year from the Shanghai Consumer Rights Protection Commission, where its sister model, the Philips AC4074, filtered 96% of PM2.5 and 53% of formaldehyde — using the same HEPA filter as the cheaper AC4072. Plus, my new comrade-in-arms in geeky air pollution testing, Thomas Talhelm, recently published his own data comparing his DIY filters against this Philips as well as the Blueair 203 — and the Philips was as good or better than the Blueair, eliminating 93-96% of PM0.5-2.5 on high speed overnight in a small bedroom. Thomas and I are on similar missions to share data with the world, and he’s even more focused on finding value — a very important and noble goal. The AC4072 is currently 2,900 RMB direct from Amazon China, compared to my Blueair 503’s price of 5300 RMB, my IQAir Pro 150 price of 9,000 RMB and my Pro 250 price of 11-15,000 RMB (depending on voltage and import status).
For my own tests, I did my usual routine: I compared real-world situations, not just blasting them on high speed all night, which I feel is an impractical and loud scenario that no one does in real life. In real life, we want the most effective machine at a reasonably quiet level. I want to know:
- How much better is the air when I’m sleeping?
- How much better is the air in my big living room, and the rest of my house, during the day?
I always compare my indoor pollution to the outside air at that time, because again my most crucial question is “how much better is my air inside, compared to outdoor air?” As I mentioned before, my current system is 80% better. Can the cheaper and smaller Philips keep up the same good results as these famous flagship models?
I was very pleased with the results. In my 13 square meter bedroom, overnight with the doors closed, the Philips AC4072 on a lower setting filtered out 87% of PM1 and 98% of PM5, when compared to the outside air. I usually have the Blueair there, and while the AC4072 wasn’t as wonderfully quiet, it was very reasonable white noise and still performed at least as well as Blueair and others in previous tests. During my last testing of Blueair, IQAir and Airgle in my bedroom, their combined effectiveness overnight was 90%, so the Philips data is right in line with that.
In my 30 square meter living room, it filtered 84% of PM1 and 96% of PM5, again compared to the air right outside my window. These numbers are very comparable to previous data, which again is impressive given the clearly smaller size and price. In last summer’s test, the living room average was 85%, so yet again the Philips is exactly in line with that data.
My Bottom Line
Despite the clearly smaller HEPA filters and unit size, the Philips AC4072 performed equally as well as all other units I’ve previously tested. Plus, it was generally quiet at most settings, and their automatic mode was quite useful for the front room. And it doesn’t hurt to be a bit sleek and stylish, occupying less than half the floor space of my other units. Regarding value, it’s half to a third the price of my current machines (same goes for the filter replacements).
That’s good news for me, and for the tens of millions of others across China who are looking for quality performance with value for money. Even this AC4072 is probably overkill in smaller bedrooms, and maybe their cheaper AC4025 or AC4012 would be fine. Besides Philips, I’m sure that quite a few models from the other major brands also would be just fine, many with prices far below the famous foreign brands. Daikin, Sharp, Panasonic, Whirlpool, Westinghouse, Honeywell, Yadu … as the DIY folks are starting to prove, all you really need is a good HEPA filter and a good fan.
UPDATE, March 2015: Please check out my buyer’s guide to air purifiers; 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.
In my seven years here in China, one of my most annoying chores has been researching air purifiers for my house — and maintaining them. It’s just exhausting to research brands, figure out what rooms need which — and of course calculate what’s the best value. It’s also an endlessly annoying hassle to keep searching for the cheapest replacement filters, which are far more expensive here than in the USA. I hated feeling helpless to rely on sales pitches from just a couple of companies, so I started to do my own home testing and posting on this blog. This summer I tested a new entry to China, the Airgle series (Chinese website here). I pitted their PM2.5 flagship model, the PurePal Clean Room Air AG900, against my steadfast friends IQAir and Blueair. Which came out on top this time? Here’s my report.
The Prep Work
First, I needed a handheld machine to measure the pollution. This time, I borrowed a model called Chinaway from the team at Vogmask. This calculates the PM2.5 and PM10 concentration directly, in ug/m3. To convert this to the more familiar AQI, you need to use the online concentration-to-AQI calculator here, from the US EPA.
Next, I borrowed the Airgle from the local vendor (started by Charlie Thomson, our local Aquasana rep). According to their website, it “features a 40 sq ft cHEPA filter with an efficiency of over 99.991%”. I then spent two weeks comparing this to my home’s five (!) machines: two IQAir Health Pro 250 models, one IQAir Health Pro 150, one Blueair 501 and a Blueair 403. I rotated all of them through four different rooms: my kitchen, the living room, and two bedrooms. Then I recorded the PM2.5 a couple of times each day and entered all the data into a gloriously complicated and colorful Excel spreadsheet. Since I didn’t have a “test room” this time, I compared each room’s PM2.5 with the outdoor air at that same time (outside my window).
The Main Conclusions
1. General protection was good with all: Wouldn’t it be wonderful to eliminate 80% of your lifetime exposure to China’s pollution, at all times? How about 90% or better when you’re sleeping, which is one third of your life? I think that’s a pretty darn good goal — and my tests showed overall efficiency of 84% using all models together, which I feel is extremely reassuring. While the outside PM2.5 averaged an unhealthy 84 ug/m3 (AQI of 166), my indoor PM2.5 was a much better 13 ug/m3 (AQI 53). Think about that — my newborn child, since he’s almost exclusively at home, has a sharply reduced exposure to China’s air pollution during his entire childhood here in China, thanks to air purifiers.
Here’s the overall efficiency for each model:
- Larger models: Airgle AG900: 85%; IQAir 250 #1: 78%; IQAir 250 #2: 79%; Blueair 501: 81%
- Smaller models: IQAir 150: 83%; Blueair 403: 80%
As you can see, all the larger models were about equal effectiveness, getting 78-85%. The Airgle did the best, but given the homemade statistics of my sampling, it’s difficult to state if this is truly a better machine. But in either case, it worked at least as well as the other models.
2. Bedroom Results: As I’ve mentioned in previous results, you can instantly eliminate one third of your lifetime exposure to China’s pollution simply by using a good purifier in your bedroom and closing the doors while sleeping. All models were on their quieter settings, providing a nice white noise in the background which I actually like. Here are my results this time:
- Master bedroom: doors closed overnight 90%; total average 84%
- Small bedroom: doors closed overnight 88%; total average 89%
I mostly worry about protecting my six month old son, so I am pleased that his bedroom was 90% protected at all times. Some morning readings approached 99%! But you certainly don’t need the flagship models in a small bedroom: the smaller models were perfectly fine.
3. Large room results: My open kitchen, dining room and living room are all connected, so it’s been difficult in the past to properly filter these rooms. I recently added a second IQAir 250 to join its older sister in the front, and I am very pleased that my results prove that I finally have good coverage, hitting that 80% goal for the first time in my three tests over the years. The further good news is that all combinations of the larger machines did well. The Airgle also did very well, and is much quieter than the Blueair 501 at the maximum speeds. Here’s the data:
- Living room average: 85%
- Kitchen average: 82%
Sometimes the PM2.5 levels shot up, especially with Chinese cooking (also candles and incense!) and cranking them all up would bring levels down. But at max settings, I’d have to give Airgle kudos for having the quietest volume at max speed.
My Bottom Line
Clearly the filtering technology in the Airgle and the IQAir are superior to the Blueair, as they both have closed HEPA filters which literally filter essentially 100% of particles even smaller than PM2.5. Both models got a very impressive PM2.5 reading of zero (100% efficiency) when I held the monitor right at their outflow of filtered air. But as my results show, it’s not just about the HEPA filter, it’s also about air flow rates and CADR results. Blueair was a solid performer in my tests even with their lower-CADR Smokestop filters — which weren’t even brand new, by the way (8 months old). But I’m sure you can argue that a better HEPA filter is preferred for China’s harsh environment, as there are plenty of other pollutants and VOCs which may be much better handled with a better filter.
Actually, one could argue about a lot of variables with these machines, especially value. And the prices of both Airgle and IQAir models in China right now are super expensive, and there’s just no way I will be convinced that it’s all about taxes and shipping extras. Sure, every commercial product has premium brands, but the markups boggle the mind. The Airgle models sold in China are made in China, and they are far more expensive here than the ones in the USA — which are exported from their South Korea factory! The Airgle AG900 in the USA is only 5,518 RMB ($900) on Amazon, a small fraction of the 17,990 RMB price here in China on their Taobao store. I personally think there’s a lot of pure corporate greed going on in this industry, taking advantage of Chinese consumers’ fear and demand. It may be legal, but it’s not ethical, and it really irks me that the world’s most vulnerable populations, much poorer and in far more polluted cities, are forced to spend far more to protect their health. It’s no wonder everyone’s reading about an American’s testing of a DIY air purifier for 166 RMB! I also recommend that consumers check out an excellent comparison from Shanghai of two dozen models, including prices and results from PM2.5 and formaldehyde.
But don’t get too bogged down on the sticker shock — in general, you do get what you pay for. And don’t forget to factor in the replacement filter costs, which can easily cost more than the original machine when stretched out over a 3-6 year window.
I am honestly very impressed with Airgle’s technology, style, solid build and quietness, but I already have a bunch of purifiers. If I had to start all over again, I think both the Airgle and the IQAir top models would be great for my large front rooms and kitchen. But right now my two IQAir 250’s are doing just fine — and the newest models are reportedly even more efficient and quieter, which would be nice. My IQAir 150 remains in little Alex’s bedroom, and the Blueair 501 quietly hums away in our bedroom. No matter how the wind howls outside, no matter what the next airpocalyse will bring, we sleep safe and sound.