在知乎上有人问负离子空气净化器是不是真的有效。我觉得这个问题很重要，因为现在市场上都是负离子空气净化器。
经常也有人给我转发这类产品介绍，问我这样的机器是不是有效：
净化神器！Wow! 30秒钟就有洁净空气吗？而且能去除甲醛？CCTV认可？卖过5万多台？太棒了！比DIY空气净化器还便宜有效，我也要一台。
负离子发生器的工作原理是什么？
不过话说回来：为什么会有人卖这种产品？是蒙人的吗？
假如这是我的北京卧室，卧室里有负离子发生器，空中有颗粒污染物：
负离子发生器开机之后，机器会发出负离子：
因为静电，这些负离子会让颗粒附着到墙上、床上、地上：
如果有空气测试仪，会显示空中的颗粒比以前少。成功了！
等一下#1
科学研究发现，市场上的负离子发生器不够强，基本上起不到作用。如果要起到作用，需要用特别强的负离子发生器–需要比市场上的要强。
等一下#2
OK, 如果普通负离子空气净化器没作用，我们也可以用一个更强大的。问题是，那么多负离子会产生臭氧。而臭氧对人有害。
等一下#3
即使你不在乎臭氧问题，你也应该发现到这些颗粒没有被过滤掉。负离子净化器只是让这些颗粒物贴到墙上、床上、地上。我想让这些颗粒附着在我的床上吗？
有人测试过北京的空气污染，研究这些颗粒到底是什么。除了灰尘以外，这些颗粒还包括铅、镉和砷–我不想让这些颗粒附到我的枕套上！
就算我不介意让这些颗粒附到我床上，还有另外一个问题。假如我回家:
划重点
下次如果有朋友给你转发“净化神器”，记得屏蔽这些信息。
Smart Air
有已经被验证过的净化器配件：HEPA滤网。HEPA能捕捉这些颗粒，而不是让它们贴到床上。这是我用Dylos测试仪在北京做的一个小测试：
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Hi. The writer seems to be unaware of the latest developments where the nee ionizers are powerful enough to emit 100 trillion ions/ second. And yet the Ozone emissions is certified to be kept well below permitted level. And can bring down PM 2.5 than increase it. They are also certified to be effective on Covid 19. They are much capable and safer than HEPA filters
Great point Rajesh. Indeed, there are more and more ionizer companies coming out with purifiers that claim to be
a) Within the permitted level of ozone
b) Effective against COVID-19.
However the truth is that even if they are within the permitted level of ozone, they can still be producing ozone. And what’s more, data shows that ionizers can increase the concentration of dangerous chemicals in the air.
If you can point to any peer reviewed data that shows that ionizers can remove COVID-19 from the air and reduce COVID transmission rates, then please send that through, it would be great to see that! However, without that we simply cannot recomment ionizers as a solution. The US EPA says the same thing: there is little research on these ionizers and COVID, and they can produce ozone.
Thank you so much Thomas for creating this website and showing concern for health of people around the world. This website gives a through knowledge of pollution and air-filters -how they work, which one is better. Very thankful to you. Keep up the great work ! Have a great day!
I got my first ionizer about ten 10 or 12 years ago. My second two or there years ago. I bought it to balance the atoms so the air was neutral so the air was purified rather than just particulate free. I was concerned about fumes gases carbon monoxides etc. I was pleasantly surprised that I had less dirt dust weird smells etc. Have one in each room and can tell a big diff when i use them and would not be without them
Thank you for the article. I was not clear on the subject!
What is the meaning of PM2.5 or PM10?
Great question! Here’s a short explanation of the difference between PM2.5 and PM10: https://smartairfilters.com/learn/smart-air-knowledge-base/pm10-vs-pm2-5-whats-the-difference/
Even shorter: PM2.5 = particles ≤2.5µm, PM10 = particls ≤10µm.
Breathe safe!
Please doctor Thomas, which one do you recommend?
none, they produce ozone and some of them up to 80ppb which is the start to where lung behaviour is affected by the molecule. The risk isn’t worth it
There seems to be a difference between ionic air purifiers and ozone generators (https://en.wikipedia.org/wiki/Air_ioniser). Are you not exaggerating saying that all ionic air purifiers release ozone?
I have a panasonic nanoe-G Air purifying air conditioner in my apartment and as far as I can find information online, it does not release ozone, does it?
Hi, thanks Ian, i’m interested in the reply to this question.
Put simply, ionizers produce ozone. The Panasonic Nanoe-G doesn’t seem to use the word ‘ionizer’ anywhere in the marketing material (perhaps because of the bad rep ionizers have), but here’s a refernce to Panasonic’s air-conditioning general manager Tomoki Miyamoto saying “It’s an ioniser“.
All ionisers produce ozone. The Wikipedia article linked to states that “Even the best ionisers will also produce a small amount of ozone”. While the amount of ozone generated may be small, and within ‘safe’ limits. Adding any form of pollutant to the home isn’t ideal.
That is simply not true. And you cant render ionizers as not feasible because some are too small to have an impact. I have after significant research been using LightAir IonFlow, which is backed by 7 years of stringent independent scientific testing, the results of which were published & released by Nature.com, (Winner of the Nobel Prize)
They state: This device generates approximately 35 000 billion electrons per second (www.lightair.com) with a steady-state ozone concentration below the detection limit (0,002 ppm) as tested by VTT Technical Research Center of Finland.
Link to full report: https://www.nature.com/articles/srep11431
I’m actually afraid of ozone hurting my pets
I read that HEPA filters cannot capture PM 2.5, is this right?
Definitely not, Chris! HEPA filters can capture over 99% of all particles above and below 0.2µm. That means PM2.5 is definitely included in the types of particles HEPA filters can capture. Check out this specific article on whether air purifiers can capture PM2.5
I am looking for a reasonably accurate and priced PM2.5 tester for use at a small school and my home. Under $200?? can you help. There are many out there.
Yes, you’re right! There are so many air pollution monitors on the market it makes it difficult to sort through them. We did some tests on three reasonably priced air pollution monitors, you could check out that review!
I have had great experience with a from Taobao, which I validated against official measurements. I suppose the entire line uses the same detector and circuitry, so while individual experience may vary, it’s worth trying at roughly 140 CNY, 20 USD.
https://item.taobao.com/item.htm?id=578487155548
I only validated its PM2.5 measurement.
It’s the VSON Technologies WP6910.
http://www.vson.com.cn/Product/0239474841.html