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Old 04-07-2020, 07:43 PM   #1
Nguyen
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Join Date: Nov 2005
Posts: 390
In case you are making a mask.

Hello, I am not sure if this thread belong here, feel free to move where ever appropriate. PM for bigger images. Thanks.

- Nguyen

Disposable surgical type mask

Material: 8x11 paper, napkin (vanity fair everyday casual) , tape, rubber band, ruler, scissor

Procedure: make sure your hands, tools, supplies, work surface are pathogens free. Start from pic 1 to pic 24. Mark one surface with letter “I”. Yellow circles with letter I (inside) denote surface orientation for folding. Folding in Pic2-Pic3 creates creases to contour paper to face. After Pic3, flip paper over and fold horizontally 4 times, creating creases for z fold later. Pic 8 is from folding “Pic 7” end to end with “I inside”. Pic 9 came from folding “Pic 8” left-to-right. Note “I faces down” in pics 13-18. Note first of Z fold toward you in Pic 18.

By wrapping the entire paper in several layers of “saran wrap” before starting step in “Pic 2”, and tape packing tape around edges (both sides) of breather hole before installing filter (Pic 18), a reusable version of this mask can be made. Sanitize after each use by spraying alcohol and leave for a day or two. The paper filter is replaced by tape in a new one.

During wear, adjust how much to unfold at the top to position breathing hole with respect to nose. I recommend max unfold and leave one “panel” at the top. This position the filter way below the nose. The first few breaths draw air from top, causing a suction creating a seal above the nose. If you wear glasses, push the top center ridge all the way up to almost between the eyes, this prevent fogging. Since there are possibilities that the environment and/or yourself have the virus, Once you put a mask on, it should be considered a biohazard. For me, it’s very difficult to have a proper procedure and discipline to store, sanitize, and reuse a mask correctly. Just think about where would you put it right after taking it off, face down or up, in your pocket, on the dash, etc, all are bad. Hence this mask design, cheap and hopefully easy to make, use once and responsibly discard.

Since you are wearing a mask, you have some belief that either the external environment or yourself carry viruses. Once you put a mask on, it should be considered a biohazard item. For me, it’s very difficult to have a proper procedure and discipline to store, sanitize, and reuse a mask correctly. Hence this mask design, cheap and hopefully easy to make, use one and responsibly discard.

Filtration test of common household material v.s N95 and Commercical Blue Surgical Mask


In my search for readily available material to make N95 masks for local nurses/doctors, I ran a number of experiments as shown in the pics. This was very crude set-up and experiments. But good enough for what I needed. I was surprise at the result from the commercial blue surgical mask, so I ran the test twice and got about the same result. So if your goal is to make something equivalent to a common surgical mask, a two layers high thread count tightly woven quilt fabric mask is good enough. If you are making a mask with removeable filter insert, be sure the insert extends all the way to the edges and “seal” with the “pocket”. Leakage between the mask and skin, or leakage between the filter insert and “pocket” defeat filtering purpose. Note effect (yellow stain in the middle) of seal leakage in Fig13, the 3M N95 did the best job, but to no avail if there was leakage. Closest to the N95 were Fig 10, 11, 12, 17.

Test set-up: paper cup with bottom removed, connected to ducted fan, inside shoe box. For each filter test, fan ran and suck out smoke through the cup with filter at the end, at constant speed for 5 minutes with box’s lit closed and incense stick burning. Incense stick smoke particles are about 0.13 – 0.28 micron, about the size of a very small respiratory droplets. Covid-19 virus size WITHOUT surrounding mem 0.07 – 0.125 micron. Fig18: N95 mask under test, Fig19 homemade mask, Fig20: smoke in box without fan running for 3 minutes.

Result: Fig1 smoke particles captured before any filtration; Fig2 after 1 layer of (LO) PT; Fig3 after 4 layers of PT; Fig4 after 1 LO PT and 4 LO TP; Fig5 after 4 LO N; Fig6 after 1 LO bamboo cloth and 4 LO N; Fig7 after 1 LO PT and 8 LO TP and 1 LO PT; Fig8 after 2 LO TB; Fig9 after BS; Fig10 after 8 LO N; Fig11 after 1 PT 1V 4 TP 1 PT; Fig12 after 2 LO N 2 V and 2 N; Fig13 after 3M N95; Fig14 after 2 LO ST; Fig15 after 2 LO woven cotton fabric for quilt; Fig16 after home made mask with another woven quilt fabric with 2 LO ST insert; Fig17 after 4 N 2 LO quilt fabric in fig 15.

Legends: PT – paper towel; LO – layer of ; TP – tissue paper; N – napkin (vanity fair everyday napkin); TB – Tool Box blue towel; BS – commercial blue surgical mask; V – white layer of Oreck CELOC vacuum bag; ST – Scott Blue towel;

If you are using vacuum bag or any of its layer, be sure it does not have fiberglass. I could not tell visually between fiberglass strands and poly fiber. I could only tell by burning a piece of fiberglass cloth and poly fiber which I happened to have. Fiberglass took longer to start burning and burned slower. I believe V above is poly fiber. For mask that uses paper clip or wire be sure to bend the two ends of the wire “back” to blunt the pointed ends. I wouldn’t use wire mask for children, accident might cause the wire to poke their eyes. If you are using reusable mask, be sure to understand what to do with it right after taking it off, I think you must assume it’s contaminated.
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Old 02-20-2022, 09:26 AM   #2
Nguyen
Senior Member
 
Join Date: Nov 2005
Posts: 390
Example of wearing a mask that was not sealed well.

Perhaps this is not important anymore since lots of people no longer wear mask, but I think we still got a long way to go. During the early days of the pandemic (around March/April 2020) I did a number of controlled experiments to show the effect of quality of filtering material v.s air gaps in a mask. Yesterday I accidentally created a real life example of how a not well sealed mask would allow virus to easily get in. As you look at the images and read the text, keep in mind that air or liquid moves along the path of least resistance.

For about half an hour I was cleaning the fireplace and chimney while wearing a KN95 mask in the attached photos. I was totally aghast in looking at the mask after the job. Notice the two black spots INSIDE the mask where my nostrils were. Note there was no corresponding black spot on the OUTSIDE of the mask. Those black spots were soot particles that I breathed out. If the mask did a good job, one would expect the exact opposite. i.e black spots on the OUTSIDE only. What happen was soot particles slid/slipped on the outside of the mask due to a combination of the mask’s CONVEX outside surface, filtering layers, and inhale suction. These particles and those right next to gaps that were around the nose (imperfect seal even with pinched nose wire), cheeks, and chin were sucked in on each of my in-breath. With exhale pressure, some (or most) of the soot particles in my lung, nose, and inside the mask were forced out and trapped in part due to the mask’s CONCAVE inside shape, resulting in two black spots inside the mask.

Virion are much smaller than soot particles, though they are in respiratory droplets. Some droplets are smaller than soot particles. So no matter the quality of a mask’s filtration layers, if it’s not sealed around your face, virus will get in.

Nguyen
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