How we searched for virus filters

Many have heard that Decathlon handed out snorkeling masks to doctors in a pandemic, makers make adapters for them, and doctors use them in dirty areas along with filters from ventilators. It looks like this: The



trick is that there really are few such ventilation filters in hospitals. It is understandable why - hospitals did not buy them to protect doctors, but to protect patients on mechanical ventilation, or rather, even to protect mechanical ventilation devices from infection. So that the next person who gets on mechanical ventilation (for example, during surgery) does not become infected with the infectious disease of the previous one ... Such cases were in the last XX century, and in fact they led to the mass introduction of such filters.

Let us consider, relatively speaking, a terrible scenario of the development of events: there are full patients, all are coeval, and now let's say there are 10 ventilation machines in the hospital, and 10 filters are left for them. The doctor has a choice - either insert it into the snorkeling mask, or the patient in the circuit ... Who will choose the doctor? And thinking about this, we decided to check - and what if it is absolutely necessary (there is such a concept in the law) can these filters be replaced? In addition, real-life ventilation filters have become a universal format today - there are absolutely any adapters for them - at least for snorkeling, at least for a 3M mask, at least for a gas mask ...



Convenient! (Further Longrid, and many pictures from under the microscope. Sit down.)

We are never experts in the field of PPE, because of the pandemic, we encountered the problem for the first time and began to study the design of filters. They claim that there is already 99.9999% filtration of viruses and bacteria during the day.



In fact, the filter element itself is about the size of a cotton pad. The rest is a heat and moisture exchanger, which is absent on many models. At our disposal was one Turkish filter (more expensive), another Chinese (cheaper). What is it that filters out 99.9999% viruses and bacteria? These two discs are ala wadded ...



It doesn’t look like rocketsines! Let's look under the microscope (at the end of the post I will give links to sources in high resolution)!

The first two photos are China, the second two are Turkey. The magnification is respectively 50x and 100x in pairs. In Chinese, droplets are visible - I checked it in the humidifier for aerosol permeability :) (using the SDS011 sensor, see below)

In general, they are electrostatic. But we did not notice it. They did not adhere to the glass at all, unlike other samples.



Handsomely? Quite! But the threads are very thick, and the cell is large. Which is generally strange.

I have a home-made device based on the SDS011 sensor, which measures particles up to 2.5 microns flying in the air. It was a sin not to check the filter for filtering thereof. They assembled the device, found a smoker, blew it into the filter and ... It filters poorly tobacco smoke. Readings went to the maximum! Perhaps the concentration is too high - I do not know. Who knows, write.



The same thing happened with the air humidifier by the way, but there he resisted a bit. However, this filter is not intended for such high concentrations - a person is still not a steam generator. But still it is not clear - how does it filter 99.9999% of viruses and bacteria? One could assume that due to electrostatics, but something was not noticed at all, in comparison with what we checked below.

Check how the medical masks look under the microscope? Here are Chinese, in pharmacies we sell 40 rubles each. Such good masks are dense:



The threads are clearly thinner, and the cell is smaller ...

Another medical mask, blue, thin, in my opinion even bought at Fix Price:



It seems everything is straight so tight. But in fact, the gaps are quite large, and live it was striking. The Chinese mask had fewer of them.

Then we took the so-called “Petryanov’s Cloth” - professional filtering material FPP 1.5.:



Respirators are sewn from them. Here they are directly electrified - they stuck to the glass! But under a microscope, it’s still not like a mechanical ventilation filter. The thread is thin, the cell is small. Expected more, to be honest.

As a result, we took the anti-aerosol filter from the building respirator, opened it and there too - under the microscope!



It turned 5 layers. The lining in it turned out to be almost the same as on medical masks. Not interesting:



But the inner layers of the aerosol filter visually turned out to be as similar as possible to what we saw inside the IVL filters:



Thick threads, rather large cells, but high density. Yes, the filter is denser in the ventilator, but there are three of them. If put together, it looks quite like a mechanical ventilation filter.

In our test, the winner is found. It remains to think about how to charge it with electrostatics? Although perhaps this is superfluous. If you have more options that you can look under a microscope in search of filtering material against viruses, offer it! ))

Original photos can be viewed here and here .

But the filter is not enough. You need to understand that in case of emergency, the doctor can use to protect himself or, God forbid, the patient? Search on GrabCad came up with a model for printing on a 3D printer. One anti-aerosol 3M disk allows you to make two filters "ala IVL", which have become so popular in our time.





Of course, you need to understand that this is all not certified and is not a medical device. It makes sense to do such crafts only in case of emergency, when there are no official ventilation filters at hand, but they are needed! I talked with many doctors, including a fairly high status - everyone says that there are not enough filters for mechanical ventilation in a pandemic, it’s problematic to buy them now (by the way, who knows if you can buy where, write - we will buy for doctors), and there’s a lot where they can will end soon. Therefore, in fact, the idea came to try to make your collective farm. Just in case of fire! It’s better than nothing.

I hope it will never be needed and will not come in handy.

Thank you for the attention!