This is a short story about how little enthusiasm can motivate people to act and show their true love for fellow human beings. It starts on a calm and cold evening in late autumn 2019 when strange dark heavy stench started pouring apparently out of nowhere and quickly scattered around the streets threatening to choke everybody in town...
Because of the unusual chemical smell of the fog the author of this article at first thaught that there was a big industrial fire in some factory nearby but no one he contacted had any information of such events. Media kept silent. As the hours passed friends and family started texting and calling each other in panic and soon it became clear that everything was "fine" - no industrial accident, just a severe case of city smog.
Smog in the city of Nis 2020
So that's it then, said LP to himself. We are all going to die this winter.
Rolling the sleeves
Nature has its methods to get rid of this menace. Rain scrubs the pollutants and cleans up the air by expelling acidic mix onto forests causing poor trees to slowly and painfully die. But before that mechanism eventually purifies the atmosphere, we pople should by all means try not to inhale it. Researchers have devised special devices and materials able to catch smog particulates. The simplest method of all is to force dirty air to stream through a layer of filter material, which is usually done by putting a fan on one side of an empty box and filter material on the other. Voila! After half an hour or so the air in a typical room will be circulated enough through the smog catcher to become much less dangerous than it originally was. The only downside of this solution is that one has to stay indoors to survive.
At the time the eye opening event mentioned above took place, there was not much awareness about the state of pollution in the southern Europe where the author lives. Commercial air purifiers were few and far between, and extremely expensive. But because the basic idea was so simple and everything alse one can imagine putting into and onto the "purifying box" such as PM particulate meter, ozonizator, ionizator, activated carbon filter, blue blinking LED, sequence timer, BlueTooth / WiFi connectivity etc. is more or less a marketing trick, the author decided to figure out the most simplest and cheapest form and try to make a purifier for himself. If it turned out that the device worked Ok and that it was simple enough to be replicated by other citizens, the idea was to distribute plans for making it free of charge. Ideally, it should be possible for any minimally skilled person with low income to easily get hold of the necessary materials and components and reproduce the design in a single day.
After a week of searching ideas online, discussing them with friends and thinkering around, it turned out that the simplest and easiest construction method was to use a plastic or perhaps even cardboard box, a PC cooling fan and some reasonable amount of commercial PM filter material. Everything could be held together by hot glue and then sealed using silicone or acrylic wall putty.
Rendering of two DIY air purifiers
The trickiest part of the design was providing sufficient pressure drop inside the box so that air would flow into it through the filter reasonably quickly. Experimentation and a moment of serendipity have shown that a pair of PC fans put "in series" and forced to run on 18V supply voltage instead of nominal 12V could fulfill the purpose. Ideally, one would use radial fans such as the ones utilised in commercial air purifiers because they are more effective in sucking air in than radial PC fans, but such components would be very hard to get hold of by individual DIY-ers.
Click here to download the construction manual.
NGO and industry boost
A good old friend active in NGO sector was contacted. He quickly arranged for LP to give a short presentation of the project to the people from non-profit organizations and a local startup hub, and soon it received great boost on the web and social media. Over a few weeks that followed, tens of thousands of people downloaded the plans.
The most positive and quite unexpected blessing came in the form of response of one of the companies that supply industry and healthcare with air filters. In order to adjust dimensions of the purifier box that people were going to make to some standard filter material specifications, LP sent inquiries by e-mail to a few distributers. The owner of one of those companies was so touched by the idea that he shipped a few blocks of filters to LP free of charge for further "research", and decided to stand out and offer the precious meterial on huge discount to anyne wishing to make the device! Those guys even built one unit in the factory to verify the design and performance :)
Instead of a conclusion
Over the following year less than fifty people in total have build the device. That is much less than its designer had hoped for, but the score is probably not bad having in mind that today's earthlings live deeply immersed in consumerism. Usefull little manual skills such as soldering and driving a screw are becoming rear and sometimes even frowend upon by modern people.
Truth to be told, 2020 brought with it much more urgent disaster to think about than plain old slow acting smog. Never the less during that period people in ex-Yugoslavia have gradually become more aware of the bad consequences of pollution. News agencies and NGOs started talking more frequently about the problem. Governments unwillingly invested in building new monitoring stations and providing public access to real time EAQI scores. Retail stores noticed that the market was opening up for commercial purifiers and responded by offering them at reasonable sale prices.
LP and his many friends involved in this unplanned adventure wish to believe that they have given a small personal contribution to pushing the initially desperate state of affairs to cleaner and brighter side.

Two full busses of people died from air pollution while you were reading this article.
designed by LP 2021