Getting A Measure On Particulates In Stuttgart

There’s a big to-do going on right now in Germany over particulate-matter air pollution. Stuttgart, Germany’s “motor city” and one of Dante’s seven circles of Hell during rush hour, had the nation’s first-ever air pollution alert last year. Cities are considering banning older diesel cars outright. So far, Stuttgart’s no-driving days have been voluntary, and the change of the seasons has helped a lot as well. But that doesn’t mean there’s not a problem.

But how big is the issue? And where is it localized? Or is particulate pollution localized at all? These questions would benefit from a distributed network of particulate sensors, and the OK Lab in Stuttgart has put together a simple project(translated here) to get a lot of networked sensors out into the wild, on the cheap.

The basic build is an ESP8266 with an SDS011 particulate sensor attached, with a temperature and humidity sensor if you’re feeling fancy. The suggested housing is very clever: two 90° PVC pipe segments to keep the rain out but let the dust in through a small pipe. The firmware that they supply takes care of getting the device online through your home WiFi. Once you have it running, shoot them an e-mail and you’re online. If you want help, swing by the shackspace.

We love these sort of aggregated, citizen-science monitoring projects — especially when they’re designed so that the buy-in is low, both in terms of money spent and difficulty of getting your sensor online. This effort reminds us of Blitzortung, this radiation-monitoring network, or of the 2014 Hackaday-Prize-Winning SATNOGS. While we understand the need for expensive and calibrated equipment, it’s also interesting to see how far one can get with many many more cheap devices.

37 thoughts on “Getting A Measure On Particulates In Stuttgart

    1. The ESP8266 is programmed either via flashing the bin you probably found or by compiling & uploading the source with the Arduino IDE. The .ino file can be found in the following repo along with the description of the dependencies:

      The configuration (wifi settings, upload targets, used sensors) can be done once it is flashed by opening the ESP’s web interface in hotspot mode or by changing the config file. See here for more details:

  1. What’s interesting is that in Belgium they did a study on fine dust pollution and they found that speed bumps are a huge contributor since each time a car goes over one it seems to shake loose a huge amount of it.
    The interesting part is that this study was completely ignored by all the euro cities with fine dust issues.

    Meanwhile we already invented speed bumps that actually go flat if you drive at the slow speed expected and only are bumps if you speed over them. So the solution is available.

  2. The reason people drive diesels in Germany is the price. 1 liter diesel is ~20 cents cheaper than the cheapest gasoline (E10). Even though the road tax for diesel is higher, it’s still more economical if you drive more than 10000 km per year.

    1. And still most people buy them even though they never go over 10000kms. Which makes the whole pollution thing even worse, just by the engines design. Any combustion engine is just absolultely filthy as long as it’s not up to working temperature. This is especially a big issue with diesels, because they’re a bit more efficient and also a bit more heavy. More mass to heat and less heat produced by the combustion process. Catalytic converters simply don’t work when they’re not up to temperature. Same case with DPF – Diesel Particulate Filters.

  3. The Boar-part is true for some parts of Germany (south), but this is due to Tschernobyl, not Fukushima. see

    [quote]Seit der Atomkatastrophe von Tschernobyl muss in südlichen Regionen der Bundesrepublik auch auf radioaktive Belastung durch 137Cs untersucht werden, sofern das Fleisch in den Handel verbracht wird.[29] Laut einem Bericht des Telegraph ist 2014 die Strahlenbelastung der Wildschweine in Sachsen immer noch so hoch, dass 297 von 752 erlegten Tieren den Grenzwert von 600 Bq/kg überschritten und vernichtet werden mussten.[30][/quote]

    1. calm down… I only repeated what is written in the german wikipedia and clarified that this problem exists for a long time already (since Tschernobyl). I agree that Fukushima certainly did not make things better… :-(

      1. Watched (most of) that video. A very good resource on the fine-particle detector. The best part is when he correlates his values with the official stats taken at a gov’t measurement site “10 km” away. They agree very well, both in absolute magnitude and in variation over time, which gives some confidence in these $25 modules doing what they’re supposed to.

  4. Wild boar is not banned in Bavaria, but they _are_ still being tested for radiation. Ground -> trees -> acorns -> boar-meat is a slow cycle, and there’s likely to be some excess radiation for a long while. Still, it’s not like there’s any shortage. Wild boar ragout is on the menu nearly everywhere here, and I’m not sad that it’s passed a radiation test.

    This is not to say that Chernobyl was anything other than a disaster.

  5. I don’t get the “ban old cars” hullabaloo. The EU recently demanded all new diesel cars should have a “soot filter” so that instead of a cloud of large particles that get stuck in the upper airways and settle down quickly we get an even larger cloud of nano-particles that embed themselves deep in the lungs and float around forever. But hey, we don’t know what harm that does to us yet, so it must be better right? And since most measuring equipment doesn’t measure particels that small, they don’t exist, so problem solved!

    1. Problem with old cars – or old engines to be correct: NOx emissions. NOx gasses tend to react with all kinds of stuff to form nitric acid vapor and related particles. Which in turn can penetrate lung tissue, destroying it and in some cases causing premature death.

      The “soot filter” is actually called DPF for “Diesel Particulate Filter” and it’s there to filter out the fine particles. Now you might think all is fine and dandy with a filter for fine particles, right?

      No it isn’t. Because fine particles aren’t just caused by combustion. And cars aren’t the only thing emitting fine particles.

  6. Well, there is a reason why the cost of the professional PM2.5 and PM10 sensors, used in the certified air pollution metering stations, can by higher than 25K $ (you should also think about 1-2K $ per year for maintenance…). And the reason is – such 20-100$ (aliexpress prices) PM sensors cannot be a source of data for a real, scientific research. They show “something”, but this “something” is quickly going into “no reliable data” area. After few weeks/months readings are totally unreliable (even if they are somehow correlated to the data shown by real-deal equipment at the beginning).
    World Air Quality Index ( is making good work assessing the true value of cheap sensors as measurement instruments… e.g. this is the look of SDS011 measurement chamber after 6 months of work:
    And here you can also check how current readings from two SDS011 in compare the reference data: (Real Time Data chapter).
    There are many initiatives last months, similar to this Stuttgart project. The hard question is – what is in fact measured and what is real value of such project when readings are so unreliable?…

    1. At least here in germany, the pollution is meassured on a day time basis (whole pollution over one day and only PM10 is meassured). As far as I know, the SDS011 results are still very similar to the official data collected by expensive devices (like these: and they had the sensores tested by a university to check the error rate. But I don’t think there is a long time study yet. The oldest sensors are from october 2016.

      1. I am almost sure, that the ‘official’ measurements in Germany are far more complex that only PM10, especially in big cities like Stuttgart. All UE countries are subjects to conditions of ‘Directive 2008/50/EC of the European Parliament and of the Council of 21 May 2008 on ambient air quality and cleaner air for Europe’. According to this law EU countries are obligated to measure SO2, NO2/NOx, CO, PM2.5 and PM10, benzene and lead air pollutions in regular basis (what, when and in what measurement ‘fashion’ – depends on specific regulations and local circumstances).
        According to mentioned law, my metropolitan area (Poznan, Poland, about 600K people in city and about 300K in whole area) is obligated to have 2 certificated, automatic and one manual air pollution control stations (I am sure, that SO2, NO2/NOx, PM2.5 and PM10 are measured). I don’t think so that in Germany this is looking different.
        I am a bit familiar with air pollution and various gas sensors. There is a real problem with mid-price-range instruments, not only able to ‘measure something’, (well if correlated with certified readings, at least for some time), but also capable to be calibrated and maintained to keep readings reliable. In case of the PM measurements we have cheap, but not really long term reliable sensors (like these SDS011) and certified instruments with very high price tag – and nothing in between. I would not try to prove in long term a quality of measurements, pollution maps, simulations based on “aliexpress sensors”. Maybe such systems have some informational role, but unfortunately it can be disinformation in the same time.

        1. Thanks for your response. I was not aware of this EU law!
          Do you know any resources for long term tests on sensors like the SDS011? Would be nice to see how the error rate changes over time and to approximate how long one of those SDS011 can be used with a certain error rate.

          1. For now the only known to me source of valuable information about performance of cheap air pollution sensors is:
            Maybe this is not perfect source, but at least someone is trying to gather facts and evaluate these sensors in scientific way – that is why this is great work and far more interesting and valuable information than typical marketing-blurred statements from the various seller’s websites.

            Air pollution topic is very popular. There is much politics around and this also generated a market for commercial solutions (cheap ones in the first place). This is making the already difficult topic even more blurred.
            For example, I know two companies in Poland that are trying to sell they wireless solutions for air quality measuring, based on Plantower PMS 5003 (or similar) sensor – the same class like mentioned SDS011. At least in one case the company is advertising their system as solution for cities, public communities and administration authorities. This is very misleading in my opinion. If an official administration unit would purchase air quality measurement solution based on such unreliable source of information (“aliexpress sensors”), it can be very easy and officially accused of mismanagement of public funds… Public administration just cannot depend on such kind of measurements in their reports and decisions about environmental management. So we have a difficult question: “Well… so, who can? What is the value of such, possibly misleading information for society?”…

        2. ” In case of the PM measurements we have cheap, but not really long term reliable sensors (like these SDS011) and certified instruments with very high price tag – and nothing in between.”

          There is this PM2.5 instrument:

          cheap enough to send up on balloons knowing they will never get it back. Not sure what ‘cheap enough’ is though.

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