开着小米自动档,不安全的空气占86%的时间

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

 

1微米Dylos测试仪准不准? 官方PM2.5数据比较测试

dylos-1-micron-guangzhou-cover

每个考虑买空气测试仪的人都想知道,空气测试仪的数字跟官方PM2.5的数字比较怎么样。所以我买Dylos DC1100 Pro激光空气测试仪的时候,我做了美国大使馆比较测试。我把Dylos Pro放在我在南锣鼓巷的房子窗户外面70次,然后跟美国大使馆同时发布的数据比较。结果两种数字相关性很高r = 0.89(记住最高的相关性是1)。

 

那次测试是用Dylos Pro版本,但是Dylos有便宜$70的基本款。如果这个基本款一样准,那不错!能得到同样的准确性同时还可以省钱。

dylos-pro-vs-standard-cn

专业版 vs. 基本款

看正面,两种测试仪看起来一样。那区别在哪儿?

关键是它们测到的颗粒大小。专业版测到的是0.5微米和2.5微米的颗粒。基本款测到的是1微米和10微米。这意味着专业版能测到更小的颗粒。

dylos-pro-vs-standard-measurement-range-cn

政府用的测试仪叫做Met One BAM(官方测试仪的工作原理)。政府测试仪测的是2.5微米及以下的颗粒。以下是三种测试仪的颗粒范围:

guangzhou-1-micron-dylos-test-bam-cn

能看到,专业版的范围稍微更接近官方测试仪的范围。所以,我猜测专业版的结果会更贴近官方PM2.5数据。但是数据怎么说?

测试

幸亏这世界上不仅只有我这个爱收集数据的学霸。有一位在广州教书的美国人,她买了Dylos基本款,然后跟我合作做美国领事馆比较测试。

从11月12号到17号,她在她的中山大学公寓外面用Dylos基本款收集了70次数据。她同时记了美国领事馆的PM2.5数据。

dylos-1-micron-test-map-cn

结果

记得以前的测试?专业版的测试仪跟美国大使馆的相关性是r = 0.89

dylos-pro-vs-us-embassy-cn

Dylos基本款结果是这个样子:

dylos-standard-vs-us-embassy-cn

相关性= .85! 这个结果低于专业版,但是还是很高。我觉得这个结果那么高会出乎人的意料。

Dylos算成PM2.5

用这些数据,我们可以算公式把Dylos 1微米的数据算成官方PM2.5微克。比如说,WHO 24小时上限是25 µg/m³,相当于Dylos基本款的1,250。

converting-1-micron-dylos-cn

最简单的公式是:

Dylos 1 微米数量× 0.02 = PM2.5 µg/m3

如果我们用这个公式把Dylos的数字算成PM2.5微克,结果跟美国领事馆的数据是这样:

1-micron-dylos-formula-vs-embassy-cn

平均来说,Dylos的公式跟官方数据相差9.04微克。

结论

Dylos基本款跟官方PM2.5数据相关性很高,比专业版只差一点。不过,Dylos结果还不如我们测试的其他两种机器

测试局限

这个结论只基于一场在广州的测试。如果我们在更多的地方和更多的季节做测试,我们能得到更可靠的结论。

公开数据

跟之前一样,为了其他书呆子同胞们,原始数据都是公开的。这个链接有测试方法的细节和更多的分析

P.S. 谢谢王亦雯帮忙翻译和做图。

–Thomas Talhelm

[email protected]

thomas-smart-air

 

Cost of air pollution

Death in the Air Infographic by World Bank

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The World Bank released a new report titled “The Cost of Air Pollution: strengthening the economic case for action” and in it they detail how air pollution is now the 4th leading risk factor for deaths worldwide. That’s worse than the deaths attributed to alcohol and drug use, HIV/AIDS, and even malaria. Besides the other reasons for reducing air pollution (climate change, our health, etc.) the economic one is probably the one that will communicate the strongest to everyone as air pollution costs the global economy in terms of foregone labor income to the tune of $225 Billion each year globally.

Click here for full report.

Click here to view the infographic in higher resolution.

Air pollution has emerged as the fourth-leading risk factor for deaths worldwide. While pollution-related deaths mainly strike young children and the elderly, these deaths also result in lost labor income for working-age men and women. The loss of life is tragic. The cost to the economy is substantial. The infographic below is mainly based on findings from The Cost of Air Pollution: Strengthening the economic case for action, a joint study of the World Bank and the Institute for Health Metrics and Evaluation (IHME).
Air pollution has emerged as the fourth-leading risk factor for deaths worldwide. While pollution-related deaths mainly strike young children and the elderly, these deaths also result in lost labor income for working-age men and women. The loss of life is tragic. The cost to the economy is substantial. The infographic below is mainly based on findings from The Cost of Air Pollution: Strengthening the economic case for action, a joint study of the World Bank and the Institute for Health Metrics and Evaluation (IHME).
Flickr Photo

Is Summer Air Better than Winter Air?

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Summer is here, bringing with it clearer skies and certainly cleaner air. Right?

Summer always seems to drive out the dense clouds of pollution that suffocate many Indian cities. However, while summer air is in fact cleaner than air during other seasons, it’s still far from safe according to the standards set by the World Health Organization (WHO).

During the winter, cold air traps pollutants close to the ground, a process called an “inversion.” Summer heat prevents this inversion, which does improve the air quality. However, average air conditions in India are still clearly not ideal.

Here’s a map of today’s pollution levels across India:

 

pollution levels
Source: https://aqicn.org/map/india/

 

On a day like today, when the AQI in Chennai, Hyderabad, Kolkata, Mumbai and New Delhi is in the ‘unhealthy’ or ‘very unhealthy’ range, we often wonder at Smart Air if the pollution in summer really is any better than the winter.

We got to the bottom of it by analyzing the US Embassy’s data in New Delhi and US consulates’ data in Mumbai, Chennai, Hyderabad, and Kolkata. So is summer air really better than winter air? We took the data from the past two years (June 2014 to June 2016) and broke it down into four seasons: winter (December to February), summer (March to June), monsoon (July to September), and post-monsoon (October to November). Next, we calculated the average particulate pollution (PM2.5) levels for each season.

Across the five cities we looked at, PM 2.5 levels were 26% better in the summer—118 micrograms in the winter compared to 49 micrograms in the summer. That means summer air is better.

Let’s take a look at the difference in PM2.5 between the five cities during different seasons:

 

 

US Embassy Air Quality Data
U.S. Department of State Data, June 2014 – June 2016. Air quality data may not be validated or verified

 

But how good is “better?” Here in India, “better” is nowhere near “safe.” Over the course of the two years we analyzed, average annual pollution levels in all five cities never fell below even the WHO’s more lenient (24-hour) exposure limit (25 micrograms per cubic meter). In fact, the average pollution levels across all the cities we tested was about 500% the WHO annual limit (10 micrograms) and 200% of the more lenient 24-hour limit (25)!

 

The lowest summer pollution level we found was Chennai (31 micrograms). But even that lowest summer level still surpassed the WHO limits.

Below are the 2-year graphs for each city. You can see that each city has two distinct swells in PM2.5 levels during the winter, each followed by 2 clear dips during the summer. Interestingly enough, comparing the summer and winter levels of each city from 2014-2015 to 2015-2016 shows some cities’ PM2.5 levels improving, while others’ increase between years. Most notably, Chennai’s winter pollution levels dropped significantly between years as did Hyderabad’s, while New Delhi and Kolkata experienced clear increases. However, we’re not sure whether or not this improvement and worsening of PM2.5 levels can be attributed to cities’ environmental efforts (or lack thereof).

The conclusion? The evidence is quite clear: summer air is in fact better than winter air. However, despite all the blue skies and warm days we’ve been having lately, there’s still a need to protect yourself inside and outside the house. Don’t mistake “better” for “safe.” Neither summer nor winter air meets WHO health standards and summer air is still of significant concern to public health.

 

Chennai US Department of State
U.S. State Department Data – June 2014 to June 2016. Data may not be fully verified or validated.

 

US Embassy Air Quality
U.S. State Department Data – June 2014 to June 2016. Data may not be fully verified or validated.

 

US Embassy Air Quality Data
U.S. State Department Data – June 2014 to June 2016. Data may not be fully verified or validated.

 

US Embassy Air Quality Data
U.S. State Department Data – June 2014 to June 2016. Data may not be fully verified or validated.

 

US Embassy Air quality data
U.S. State Department Data – June 2014 to June 2016. Data may not be fully verified or validated.

 

cars delhi

A $3 billion pollution ‘solution’ in Delhi – but will it work?

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Last week, the Ministry of Urban Development announced a Rs. 19,762 crore ($2.95 billion) solution to reduce vehicular pollution in Delhi. If approved, the proposal will seek to reduce emissions from the over 8.8 million vehicles in the city, mostly owned by the rising middle and upper classes.  Despite this class differential in vehicular emissions, some of the improvements sought include:

  • Seven pilot parking management districts
  • An integration of  207 metro stations with other forms of public transit systems
  • Construction of cycling tracks and footpaths with crossings at least every 250 meters, with first use of street space to pedestrians
  • Removal of choke points across the city
  • A procurement of 2,000 new buses immediately and 4,000 new buses in the next phase
  • Development of a Bus Rapid Transit System on high-density routes
  • Parking fees and congestion tax to discourage private vehicles

While several of these suggestions, namely parking management districts and imposing congestion taxes, may curb vehicle use, the rest of the plan largely ignores the intersection of class and the environment in the city. Academics such as Asher Ghertner and Sunalini Kumar have argued that past environmental efforts in Delhi have largely failed due to “bourgeois environmentalism” wherein middle class biases and interests take over environmental efforts that are genuinely in the public interest.

This may very well be the case with the Ministry’s air pollution proposals, which largely focus on bus and metro expansion. In today’s age, car ownership is no longer a practical necessity but rather a symbol of class, prestige, and status. In 2001, Delhi had 900,000 registered private cars. Today, there are more than 2.6 million. Though small in comparison to the city’s population, the increasing use of cars in a deeply congested city is unlikely to be deterred by  building new bus and metro routes. In fact, the Supreme Court acknowledged the problem in January when it asked DMRC to explore the option of creating a ‘premium‘ class service on the Delhi Metro to make the train seem more friendly for the wealthy.

We’ve already seen a big failure in convincing the middle class to use public transport through the Bus Rapid Transit system in 2008, which displaced cars from three lanes to two and dedicated a special lane to bus use. Rather than getting support, the BRT received a hugely negative and critical media campaign by middle-class journalists who lived in colonies along the route. Their complaints centered on the fact that the special bus route increased car travel times by 20 minutes or more, leading to inconveniences for car users. This argument went to the Supreme Court when an activist argued that the BRT system ignored the “wealth creators” of the city who preferred cars. It seems that these reactions to public transport have gone unnoticed in the latest proposals.

Also ignored are larger contributors to air pollution than cars—trucks and two-wheelers—which contribute to 24-25% and 18% of PM 2.5, respectively. Cars, on the other hand, contribute to 14-15%. While public transport may attract owners of two-wheelers, typically lower-middle class, it won’t make big progress in changing truck usage. Policies considering trucks and two-wheelers seem absent from the proposals.

Ultimately, Delhi’s air pollution solutions need a broader perspective and incentive model that accounts for the behaviors driving modes of transport. If Delhi is to curb pollution, it needs to create marketing and norms to get managers, CEOs, members of parliament, and other middle- or upper-class individuals to prioritize public transport. The idea is not as crazy as it sounds; such consumers readily take on public transport in cities like London and New York. However, behavioral nudges must come along-side policies that disincentive car ownership by higher costs to purchasing cars, especially second cars. A prime example is Singapore’s Vehicle Quota System, which makes vehicles 3-5 times the actual cost, thereby incentivizing people to use public transport. The same must go for two-wheelers, and strict environmental regulations must be put on exhaust of all vehicles, including trucks.

It’s time to create norms that are set for everyone, not just the poor. Just as lower-class auto drivers have been forced into using CNG to curb pollution, and over 3 million squatters have been evicted from their land for ‘polluting’ the land, it’s time to create policies that promote the middle- and upper-classes to create a better environment. Though increasing public transport is well-intentioned, it is not the answer. The Ministry of Urban Development must take into account deeper considerations of culture, behavior, and norms and use the increasingly expanding world of marketing and behavioral economics to change what is normal.

 

 

heart

Air pollution can break your heart

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For years, air pollution has been linked to heart disease but scientists haven’t been able to understand how, exactly, it breaks your heart. Last week, researchers in the U.S. released results from a long-term study that shed light; they found that air pollution thickens blood and hardens arteries, accelerating atherosclerosis — a disease in which plaque (calcium, fat, cholesterol and other substances) builds up in arteries, preventing oxygen-rich blood from reaching organs or body parts. This leads to the development of other diseases based on which arteries and body parts are affected, including heart attacks, stroke, or even death.

The study tracked 6795 participants in 6 U.S. cities between the ages of 45-84, all without a previous history of cardiovascular disease. Participants ranged from four ethnicities and came from a variety of socioeconomic backgrounds. Researchers then scanned participants’ arteries over a course of 10 years.  At the same time, they measured concentrations of PM2.5 and traffic-related gases called nitrogen oxides (NOx) outside participants’ homes, while creating estimates for the concentrations of pollution participants inhaled during time spent indoors.

The study found that PM2.5 and NOx were strongly associated with the build up coronary artery calcium, which accelerates atherosclerosis. Joel Kaufman, the lead author and a professor at the University of Washington, explained to ThinkProgress that air pollution may trigger cell inflammation, affecting white blood cells that protect the body against infectious diseases. As white blood cells accumulate, they build up plaque, causing atherosclerosis. This mechanism may explain why air pollution has also been linked to cardiovascular problems and mortality.

In the study, participants’ pollutant concentrations between the years 2000 and 2010 ranged from 9·2 to 22·6 μg/m³ for PM2.5 and 7·2 to 139·2 parts per billion (ppb) for NOx. For every 5 μg/m³ increase in PM2·5 and for every 40 ppb increase in NOx, coronary calcium deposits progressed by about 20%.

Though the results of the study are sobering, it’s important to note that the study was done in the U.S. under air pollution levels that fall well below the World Health Organization’s recommended PM2.5 exposure of 25 μg/m³.

Comparatively, North Indian cities tend to have significantly higher annual average PM2.5 levels, with Gwalior at 176, Patna at 149, and Delhi at 122. Further research needs to be conducted to understand how such high levels impact the severity of plaque build up and heart disease. However, a comprehensive Global Burden of Diseases, Injuries, and Risk Factors Study calculated that about 5.5 million people prematurely died in 2013 because of indoor and outdoor air pollution.

 

Feeling the heat? You’re feeling the pollution too.

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Had trouble breathing lately? It might be because despite popular opinion, Delhi’s air pollution levels aren’t doing so great in the summer heat.

Our team regularly monitors air quality through the Air Quality Index Widget on our phone, which uses U.S. Embassy Air Quality data. The U.S. Embassy converts P.M. 2.5 (mg per cubic meter) to an Air Quality Index (AQI) to easily guide health decisions. It is fairly typical for Delhi figures to be in the orange or red zone, considered unhealthy at an AQI of 151 to 200, in the summer. Winters typically see figures in the ‘Very Unhealthy’ violet category with an AQI ranging from 201 to 300.

US embassy AQI
U.S. Mission NowCast Air Quality Key

 

Though April AQIs have been, on average, showing moderate AQIs below 100, the pollution levels in the last week of April spiked.

April 28th, 29th, and 30th averaged at ‘very unhealthy’ levels of air pollution with average AQIs of 248, 246, and 300, respectively. Such high levels of pollution can cause significant aggregation for those with heart or lung problems.

The highest hourly averages on these days were above 500, with the maximum of 592 on 29th April. To put this into perspective, the U.S. Embassy Air Quality key maxes out at 500, which marks the maximum in the worst category, ‘hazardous.’ Hazardous levels of air pollution may cause serious heart and lung risks, even leading to mortality amongst those with cardiopulmonary disease. At levels above an AQI of 500, these effects may worsen.

Though there are is no evidence to help us understand the unusual spike, the high amount of air pollution may be a result of two on-going activities. One, the end of April brings an end to the wheat season. To clear the land of wheat stubbles in preparation of planting other crops, farmers often burn the wheat residue. According to Umendra Dutt of the Kheti Virasat Mission, however, only 16% of wheat reside is burned, so it is unclear how strongly the activity contributes to the PM 2.5 levels. Two, water-parched areas in Uttarakhand have resulted in an unusual number of forest fires. As of last weekend, 427 fires were simultaneously burning in the region, with reports of air pollution and poor air visibility.

Though the reasons for the poor air quality is unknown, Delhi government has yet to put precautions in place to protect public health. Contrastingly, China has frequently triggered red alerts in cities across the country when smog levels rise to unusual levels. Red alerts, which include recommendations that people should stay indoors and vehicles should be restricted, are issued when regions see an AQI of 300 or above. Delhi is seeing almost double this number during peak pollution hours, yet the government has taken limited precautions beyond odd-even. Until institutional factors are not addressed, air pollution will persist in high amounts. Such factors include industrial policies in Delhi and neighboring regions, implementation of policies restricting crop burning, and measures to reduce negative health and environmental impact of droughts.

Does Spring bring better air to Delhi?

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Spring in Delhi, is the air clean?
Spring in Delhi, is the air clean?


Delhi Winters are notoriously known for bad levels of air pollution, but we often hear that air gets cleaner come Spring. We were curious what was happening in our own backyard, so we put out our Dylos Particle Counter on a rooftop near our Saket office.  The Particle Counter measures particle counts between 0.5 to 2.5 micron in size per 0.01 cubic ft. From this number, we can estimate PM 2.5, which are microns approximately 30 times smaller than human hair. PM 2.5 is considered harmful to human health since these particles can get lodged deep into the lungs and cause respiratory and cardiovascular problems.

Here is the data from November 2015 – March 2016. Though air pollution levels do drop in March, notice that the month still had zero days of ‘good’ or ‘moderate’ quality air. Due to fluctuations in hourly air quality, some of the maximums in March are higher than the average pollution levels between November and February.

Though Delhi air may get better in the Spring, it doesn’t improve enough to be considered clean or healthy. Keep those masks and air filters handy!

Smart Air Filters featured in The Hindu

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On March 31, Smart Air Filters was exclusively featured in The Hindu’s Business Line. In “Making cleaner air affordable the DIY way,” Chetna Mehra highlighted our commitment to providing clean air at a low-cost. Here’s an excerpt from the article – you can read more here.

If you are living in Delhi, you are already deprived of clean air, and may be ready to pay a hefty price to get lungfuls of this precious resource. But how much should clean air cost? Most will say it should be free; but the most affordable tag on it now is ₹3,400.

Social innovation firm Smart Air is selling affordable DIY (do-it-yourself) air-purifiers that clean indoor air as well as any expensive air-purifier available in Indian market in the ₹16,000-30,000 price range.

To find out more about our range of clean air products, check out our online shop.