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:
Bottom Line
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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