How I made a KN95 respirator at home from improvised materials. detailed instructions

Against the background of this situation with coronavirus, a week ago I decided to purchase several respirators. At home I had one, KN95, class ffp1, I wanted to buy a few more with an exhaust valve and a higher class. But bypassing several construction stores, I did not find anything at all there - they all sold out a month ago.

In the end, I decided to direct my efforts in the other direction and make a respirator on my own out of improvised materials.

I did not find normal instructions for making a respirator on the Internet. There was only an article on Habré how to make a surgical mask and even videos on YouTube how to sew a mask from a fabric.

After weighing my capabilities, I realized that I could not make a respirator with an exhaust valve at home. It was unrealistic to make a normal valve from improvised materials. There was an idea to print on a 3D printer, but because it was necessary to make a drawing, experiment with materials, and this all the time, I refused this venture.

For the sample, I took the KN95 respirator, which I had:



I decided not to completely copy the design, but to modernize it a bit. In my version there will be an additional layer of filter cloth.

I took my piece off my respirator and went shopping for materials. All I could find was agrofibre. It was of two types:



I took a denser one (in the photo on the right).



I also found a non-woven filter cloth with a thickness of 5 mm.





If you have no opportunity to buy such a fabric, then you can try to use viscose towels as an additional filter layer, folding them in several layers.



In addition to the fabric, I also bought elastic, foam rubber and baking paper.

In order to solder together the layers of agrofibre, as on the original respirator, some kind of roller was needed. At first there was an idea to take the gear, but did not find a suitable one. Therefore, I bought a plumbing fitting. First sawed off the thread. Then, holding a drill in the cartridge, he turned it with a file. Then he marked out and grind the teeth with a file.

It was possible to try to solder agrofibre with an iron, but I thought that a roller would be more convenient.



The resulting roller was put on a bolt with a length of 100 mm, fixed with nuts and made a handle from a piece of wood so as not to burn his hand while heating the roller.



I decided to cut the nose clip from an aluminum bottle from a deodorant.

All the material that I had:

Manufacturing process

1. We print the drawing, paste it on cardboard and cut it out. I decided to slightly change the design of my respirator and added an additional protrusion in the pattern in the center, 2 cm wide and 8 cm long. I also extended the protrusions on the sides. This is necessary in order not to glue the nose clip, but to put it in your pocket, and not to solder the elastic bands, but to thread them into the resulting turns.



2. Transfer the pattern to agrofibre. It is necessary to cut three blanks: one with additional protrusions, which we finished and two ordinary ones. Here's what I got:



3. Transfer the pattern to the fabric for the filter. The filter should be 5 mm smaller than the usual workpiece around the perimeter, take this into account when cutting:


from photographs, I think it’s clear what needs to be done.

4. Put it all together. At the very bottom we put a large blank with protrusions, then a blank without protrusions:



Apply a filter cloth on top and cover with the remaining blank of agrofibre:





5. Now you need to solder the layers of agrofibre together around the perimeter. We fix the whole “sandwich” with clothespins:



Initially, I planned to make a four-layer respirator plus filter cloth. But in the process of experiments on choosing the optimal temperature regime of the knurling roller, it turned out that the four layers of agrofibre do not solder. Normally, it was possible to solder only three layers. Therefore, in the final version of the respirator, I got three layers. If you can solder more layers, then do more. As you like and consider necessary. In principle, agrofibre can not be soldered, but flashed with ordinary threads.

After several experiments, he stopped at a roller temperature of 210-230 degrees Celsius. I found this out experimentally by measuring the temperature with a multimeter with a thermocouple.



Between the soldering roller and agrofibre, I laid baking paper so that molten plastic would not stick to the roller.
First, we weld along the perimeter, along the line, as indicated in the photo:







6. Now we wrap and solder the protrusions:



7. Fold the respirator in half and solder along the line marked in the photo:





This joint must be especially carefully soldered so as not to inhale air bypassing the filter.

8. Cut a piece of foam rubber 7 cm long and glue it from the inside to the place where the nose will be:



9. I made the nose clip as follows. I cut the bottle from the deodorant and cut off a strip 15 mm wide:





Since the aluminum from the bottle was not of sufficient thickness, folded (bent) the strip in half lengthwise: I



cut a strip 7 cm long and put it in my pocket on the respirator:



10. I cut two pieces of gum 18 cm each , slipped them into the welded gates along the edges and tied the ends of the elastic bands with knots:



As a result, I got such a respirator: It is



a little harder to breathe through a makeshift respirator than through the original one, so I concluded that it traps more particles and filters better.

Since I got more layers of filter material than in a ffp1 respirator, I think that the respirator I made corresponds to ffp2 protection class.

The drawing for the pattern can be downloaded here .