开着小米自动档,不安全的空气占86%的时间

SmartAir聪明空气

从我开始测试DIY空气净化器,我一直说安全的空气不需要花很多钱。所以小米出1,000元以下的机器的时候,我假设效果不错。我一直没有来得及测试它;我最近终于做了测试,而结果出乎我的意料。

测试

Smart Air联合创始人Anna在北京朝阳门15平米卧室测试了全新的小米2 (Mi2)机器。这个卧室是我们以前测试DIY、IQ Air, Blue Air和飞利浦的房间。Anna分别做了6次自动档测试,和6次最高档测试(小米把最高档叫做“最爱档”)。

Minion

测试很简单:Anna早上出门的时候开机;回家的时候关机,所以测试的时候,没有开门开窗走来走去的干扰。(测试方法细节和所有原始数据在这儿。)

为了算效果,Anna用了一台Dylos Pro激光空气测试仪。这个Dylos测到≥0.5 微米和≥2.5微米颗粒。我做了对比测试发现,  Dylos 0.5微米数据跟美国大使馆PM2.5相关性很高r = .90)。

和我之前做的测试一样, 为了算效果,我算了(卧室里开机前的颗粒数)比 (测试最后四个小时的颗粒平均数)。

结果

小米的结果算是我测试过最低的之一。平均来说,消除了大概60%的0.5微米颗粒在测试的最后4个小时。

Xiaomi effectiveness

下面是小米的和我在同样的房间测试过的其他机器的结果比较。

平均消除的颗粒

下面是比较正常的测试,我还加上了世界卫生组织的PM2.5 24小时上限(25微克)

小米的房间测试

小米特入自模式

数据为什么这么低?关键是,就算让小米开最高档,过了三个小时之后,它就自动调成自动模式。为了确认,我们做了过夜测试,开了最高档然后用了噪音仪看看它的“工时”。

Room

可以看到,前面三个小时一直开着高档,然后可以看到自动档的上下波动:

xiaomi 杂音

我在下面的图加上了PM2.5数据(Dylos记录的)。可以看到每次停止运转,PM2.5上升。

杂音VSPM 2.5

这些数据显示小米对“安全的空气”的定义有点太宽容。PM2.5降到40微克的时候就关机,而40微克高于WHO的上限。等PM2.5到70微克的时候才开机,70是WHO上限的差不多3倍。

真的不能一直开着高档吗?

我觉得不能一直开着高档很奇怪,所以我让Anna问小米客服两次。客服确认了,三个小时之后就自动调成自动档(整个聊天记录在实验详细页面)。

Blurred

百分之几的时间安全线

小米的自动档经常让室内的空气在安全线的两倍以上。我算了室内空气有百分之几的时间超过安全线,用了这个规则:

净化器开机至少一个小时的时候,同时外面的空气不安全(PM2.5 > 25微克),有多少小时室内空气也不安全(> 25微克)?

以这个标准,小米开机的时候,室内空气竟然86%的时候不安全。我测试过的其他大小相似的机器,结果它们7-16%的时间超过安全线。

%时间不安全的空气

也许小米使用的是中国官方的PM2.5 24小时上限(35微克)。即使如此,在小米启动77%的时间里,室内的空气污染
指数还是是属于不安全的。

等一下,你确定确定

得到这个结论我想特别小心。我看到过其他人测试小米第一个版本,然后结果不错,包括美国医生Dr. Saint Cyr的测试。(不过,我也看到报告说小米的机器有问题,比如这个人,滤网还在塑料包装里,让小米开最高档,app还说污染立刻下降。)所以第二次第三次分析了数据(所有的数据也是公开的):

  1. 我们用了别的空气测试仪在别的房间做测试。
  1. 我开除了外面AQI有任何比较大的波动的测试天。
  1. 我分析了外面AQI中度或以下的测试天(< 150微克)。
  1. 我比较了这次测试和我最近在这个房间做的测试。

这些不同分析的方式结果都差不多(在这儿)。但我必须在此声明,我们只使用了一台小米Mi2。因此,使用另一台机器的结果有可能是不一样的。我也向所有有Mi2的网友们做用这个测试方法做重复试验。

那小米怎么办?

我看到这些数据只能得到一个结论:风扇和滤网好像没有问题,但是小米的设计有问题。就算我用最高档,睡呼吸不安全的空气。这是一个很重要的问题。

只是小米的问题吗

其实我不能建议任何测试过的自动档。我也测试过飞利浦AC4072的自动档,而它平均消除的0.5微米颗粒是59%,跟小米差不多。所以我觉得问题是广泛的自动档的问题,而不仅是小米的问题。

不过,我还能推荐飞利浦。为什么呢?因为飞利浦可以一直开着中档或高档,而我测试数据显示高档的效果不错

我相信小米可以解决这个问题,只要允许我们一直开高档,而不用强迫我们用自动模式。但是小米解决这个问题之前,我不能建议用小米。

公开数据

跟之前一样,为了其他书呆子同胞们,我发布了原始数据和测试方法的细节

 

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在 “开着小米自动档,不安全的空气占86%的时间” 上有 47 条评论

  1. Hi. I am in NCR region with MI Air Purifier 2. I am willing to do a test for you but I do not have a particle counter. In case you are willing to lend a counter to me, i can do a test as per your methodology.
    PS: I am an engineer and have varied tests back in my days.

  2. same issue here. the pm sensor doesn’t seem reliable , sometime i see the number jump to 30 and fall back down… it’s always steady at 10 . well xiaomi just released a Xiaomi PM 2.5 Air Detector Portable OLED screen , it might fix things ?
    I’ve just ordered a second xiaomi air purifier . i’m going to see on how they compare, I might have a defective one
    also I find it strange that the auto on/off doesn’t work at all (schedule option on your phone)

    1. Yeah! I recently tested the Mi1 and Mi2 against four other particle counters. The results weren’t pretty. The Mi particle counter was off by as much as 200 micrograms! That’s shocking, especially when that particle counter is responsible for deciding when you need to clean the air.

      It wasn’t just high readings. It also missed on low readings. When the other particle counters were around 1-2 micrograms, the Xiaomi was still reading 9-12.

      1. I don’t think you understood what a couple of commenters suggested. The separate Xiaomi PM2.5 particle counter has the ability to control Xiaomi air purifiers. It also uses a more accurate technology for measurements than what is built into the Xiaomi 2 air purifier. A repeat test using it as the controlling device would be interesting.

        1. Aha, that standalone particle counter we’re yet to test! In the next month we’re actually going to be running a Kickstarter project to test a whole host of particle counters. This one will be in the list for sure. We’ll hopefully have results on how accurate this standalone device is in the next few months

  3. I was interested in to buy one of theses but if they always goes back to auto mode automatically after 3 hours and auto mode works so bad this machines in useless unfortionatly (I like this machine very much until I was reading this).
    This they must change, if I do not want to have auto mode is shall not switch over to that automatically!

    1. Interesting question! You mean getting under the hood and trying to code it differently? I didn’t get that technical. I just looked at the settings it has available.

      1. Paddy here, the tech nerd at Smart Air! Nice to see that there are some solutions out there, but I think for the average guy who doesn’t know Node.js like we do it might be tough to set up. Gin’s automation solution is simpler for the layman, but still not perfect. The fact that both these ‘solutions’ exist show that this is a very real problem in the first place.

    1. Hi Gin, good idea! When we ran the tests before we didn’t spot this setting. I tried this out and managed to set it up in about 10 minutes, not too bad. Whether or not we can expect the average user to do it (or more importantly know that they need to do this to breath clean air) is another issue though. I’ve attached a screenshot incase anybody else wants to set this up!

      Image: https://smartairfilters.com/en/wechatimg132/

      If you need the purifier on at other times when you’re home, or if you want to turn it off during these times, it will still require more tweaks to the settings.

      1. Paddy,

        I cannot access the screenshot.

        Kindly advise on how to keep the device running on Turbo Mode all the time.

        I have the Mi Home App installed on my Android phone.

        For everybody’s information here, I live in Delhi and on “Auto” mode the PM 2.5 estimate hovers around 60 and on “Turbo” mode it hovers around 40.

        This is not healthy. Healthy air should not have a PM 2.5 count higher than 10.

        Perhaps I should try the BlueAir Blue?

        But, I cannot put my trust in a machine that looks so cheap.

        Anyway, I have decided to stick with the Mi 2 for now.

        Any help on making it run on Turbo Mode 24*7 would be greatly appreciated.

        Regards,

        Dhruv Sen.

        PS: Have you guys tested the Blue Air Blue (maybe it is only available in India). How does it compare to the Mi Air Purifier 2?

        1. @Dhruv

          I’ve fixed the image link now.
          We have not tested the Blue Air Blue, so cannot vouch for it. One thing is that any air purifier that’s running during this highly polluted period (over Diwali) will find it hard t keep indoor pollution within safe levels. Especially if your room is badly sealed.

          Regarding your tests done in Delhi: we have also just tested the Xiaomi 2 in Delhi, and found that it left air unsafe 76% of the time. We will have the writeup finished soon. The Xiaomi 2 really is a dangerous machine.

          With the Blue air priced at Rs.23,000 you could get 3 Cannons for the same price. That will give you the added benefit of distributing your clean air sources around your your room, which should help counter the negative effect of leaky windows or doors.

          1. In reference to the screenshot, I am not able to access the “Automation” feature highlighted. Perhaps it is only available in China or on Apple phones, I don’t know. Your screenshot seems to be from “WeChat”.

            On my Android in India, all I have is a “Schedule Power on/off” feature that lets me set when the device shall be switched on or off. It does not allow me to select the “Favourite” or “Turbo” mode as it seems to in your screenshot.

            This is not a problem during the daylight hours when I can monitor the device but when I go to sleep the machine shall automatically switch to “Auto” mode after three hours. If I can find a way to keep it running on “Turbo” while I am sleeping, that would be quite useful.

            Please ask your testers in Delhi if they have the same features as you seem to in China. You must think of us Indians.

          2. Damn, that’s a shame! I’m on an Android phone, using the ‘Mi Home’ app downloaded from the Xiaomi App Store. Seems like this has its issues as well, so I guess we still can’t recommend the Xiaomi purifier as a reliable way of getting clean air. I hope you can find a solution and keep breathing safe!

        2. @Dhruv

          You can download Xiaomi Market from the web. You will need to change the permissions on your phone. Your phone will give you prompts to change permissions as you do so so it’s easy.

          Delete the Mi Home app you downloaded from Google Play.

          Open Xiaomi Market, and search for Mi Home and download.

          Change the location setting to “Mainland China” and the language setting to “English”. The automation setting is only available on the Mainland China setting.

          Re pair your Air purifier with the app.

          Voila! At the bottom of the Mi Home screen (not the Purifier shortcut) you will see an Automation option. Just remember you are working with Mainland China time.

          Some of it’s in Chinese. But it’s easy to workout. You can now program your purifier as suggested above.

    2. By the way, apparently Automation settings are only available if you select the Chinese Mainland server. It doesn’t matter that you’re actually located elsewhere.

      If you switch to the Chinese Mainland server, you will have to re-add the device.

      Not everything will be translated into English, but I think having Automation is worth the inconvenience.
      If you have an Android device, you can have the Chinese be automatically translated to your language https://thenextweb.com/google/2016/07/07/googles-now-tap-can-translate-text-android-screen/

  4. Please not with the “2.5ppm detector” you can set up different patterns easily, under condition you can understand Chinese. In combination with the MI Home app and the detector your problem described does not occur, you have excellent results. I could sent you screenshots how to set up. It is not difficult, if you can read Chinese at least.

    1. Aha, you mean with the standalone PM2.5 detector Xiaomi now sells? Linking up the Xiaomi with a reliable working detector is definitely one way to solve the problem. It means people will need to fork out an additional 399RMB for the particle counter (more than half the price of the purifier itself), but if you’ve already invested in a Xiaomi and don’t want to switch to another purifier, this is probably the most reliable way to make sure you’re breathing clean air.

  5. This is really interesting reading. I recently purchased the same purifier, not knowing about this problem. Then I tested it, and setting a custom speed with the iOS app, my machine doesn’t switch back to auto at all. Has Xiaomi updated the firmware since this was published? Can someone else verify I’m not crazy?

    I’m also trying to establish which behaviour is currently true of the ‘pro’ model, as I’m looking for something for a larger space.

    1. If it’s above a certain speed I’ve found that the machine does switch back to auto. However, if it’s below a certain speed, then the machine stays on the whole night.

  6. This is insane. So the air purifying is actually good but the way it deals with auto mode etc is a mess.

    What about the new Xiaomi Air Purifier Pro? I want to buy this one because I like to have an OLED display on the thing, so I can disable my wifi and just look at the device to see any problems with the air (I find it funny how people want clean air but want to leave wifi turned on all day to use the Air Purifiers that need wifi).

    This one still needs wifi to tweak it as far as I know since I see no buttons but the play is to leave it on auto mode.

    I just can’t find any legit tests on this one. It’s 500 bucks so I need to know if this works or it’s a scam. I need to find out if my leaky nose and dry eyes condition improves with clean air. My room is trapped with indoors windows that leads to the laundry so I don’t think it’s very good. Please help me choose the best air purifier.

    1. Anyone knows something more about the Xiaomi Air Purifier Pro? It’s very hard to find anything useful over the internet. Did they improve something there? Does it have same issues in Auto/High modes?
      I want to give it a try, but I’m affraid that noone has reviewed it and it seems it’s already on the market for 1 year.

  7. So the only reason one should not buy this purifier is becuase of it changing to auto mode after 3 hours?
    I have one more doubt – the Xiaomi’s website mentions that it uses a high density EPA filter and once it mentions it uses Toray EPA filter. Is that different from HEPA? i have already bought it. Should i return it? I live in Delhi. Can someone recommend me another purifier below Rupees 15k?

    1. I think the automation is now available in india as well. got to the screen where it shows the Pm 2.5 level. click the three dots on top right corner. Automation is available under general settings. My doubt still remains – the Xiaomi’s website mentions that it uses a high density EPA filter and once it mentions it uses Toray EPA filter. Is that different from HEPA? i have already bought it. Should i return it?

    2. I’m not sure on what HEPAs the Xiaomis are shipped with in India, but in China they are 95% effective filters. This is good enough for normal house purifying, so I would not worry about this. You can find information about comparisons of different purifiers on our homepage: smartairfilters.com/in/ We tested multiple purifiers in India, and found that they all perform just as well as each other even the more expensive ones

  8. The switching back to auto mode can be disabled by using the Schedule Power On/Off feature in the device settings in app : Simply set the purifier in favorites mode at desired setting and then create 3-hour intervals of power on-off timers like power on at 1200 hrs and power off at 1455 hrs and then another timer of power on at 1500 hrs and power off at 1755 hrs and so on creating a total of 8 timers and setting them to run everyday..Within every 3 hour interval, the purifier will shutdown for 5 minutes and then power on in favorites mode always, thereby preventing the switching back to auto mode which happens after 3 hours of running in manual (favorites) mode. Hope this helps my fellow Indians, especially Delhiites coping with severe pollution.

  9. You can always have it on high setting. Here is how to do it. Download the app and link it up to your Mi 2 purifier. You can set timers for through this. If you turn on the purifier using your phone it will go on auto mode, change it to high power mode. Then turn it off. Now turn it on and it will automatically go to high mode unless power is cut. Now you can set timers for 2hrs 59 mins. Set timer to start again 1 minute later for another 2hr 59 mins. So if you set 8 timers for 2hr 59 mins you can have clean air 24/7. I have tested with PM2.5 meter and it works.

  10. Hey,

    Your measurements show that this purifier works correctly in Auto mode. China AQI (Air quality standards) says: maximum 24-hour average 75uG/m3, Maximum annual average expose: 35uG/m3. This product is setup for this standards not US/EU or WHO which As you mention are 3 time more restricted – simple firmware update should change it easily. The question is if Xiaomi do this?

    DK

    1. We did also measure the Xiaomi against the China annual limit of 35µg/m3, and we found the Xiaomi still gave unsafe air 77% of the time! See the paragraph just above “Wait, are you sure sure?“.

  11. Im a bit new to Mi products but I just got a an air purifier 2. Mine stays on high (not turbo) as long as I want.

    I have it set to off after I leave and on before i return home. I cant choose which mode it uses during scheduling but it returns yo the last setting…so off on high /favorite turns back on to high.

    The meter seems to stay below 20 …usially 10/9 except when cooking then it reads like 90.

    So far Im pleased.

    If you have an old android. Root. Get tasker, push bullet, and remote touch/press to simulate button presses. DIY remote control anytbing as if you were using the phone yourself.

  12. First of all, excellent post. I just bought 6 of these in Pakistan, and i opened just one. Will be returning the balance 5 after reading all of this.

    My question is, if we agree that the xiaomi performs only marginally well, but at at acceptable level at the highest setting, how does the noise/decibel level at this setting compare to its peers?

    1. This is a very good question. Since the Xiaomi has only one small fan inside it, it needs to rotate at a very high speed to pull a lot of air through. This means it’s also very noisy (66dB in our tests) on its highest setting. On the other hand the Blasts we’ve created are 50dB on their highest setting, and they provide as much clean air as 2-3 Xiaomis. You can see more tests on noise in the Blast post I’ve linked to here

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