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Covid19 – DIY Mask Tutorial

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  • Thu, Mar 19, 2020 - 04:28pm



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    Covid19 – DIY Mask Tutorial

Ok recognizing that masks are going to be in short supply, I did some youtubing to see what kind of “do it yourself” options there were. I came across a video by Canadian Prepper, which turned me onto furnace filters as a filter material. Here’s the video:


First thing, a note about the filter. In his video the furnace filter is rated 1900. Here I found mine rated 3000. Don’t know what the difference is, what is important is that you get one with a MERV rating of 13.

MERV stands for “Minimum Efficiency Reporting Value”, and tells you how fine a filtration factor it has. Here is a good explanation of the standards and the way they rate.


This table shows why we want to use MERV 13 material due to its ability to get down to the range we are dealing with in this virus and its particles.

merv table

Ok, so I went down to the local big box hardware and garden store and went shopping for filters. Now my furnace uses 16x25x1″ filters. I thought I’d pick up a three pack and use one for this tutorial. Unfortunately (and fortunately as you’ll see in a moment) MERV 13 filters only come in 4 and 5″ thicknesses. Here’s what I bought, it cost me about $20US.

furnace filter

Notice it has a pleated structure, that’s to help it trap particles. Except at the edges of the pleats, incoming particles hit the material at an angle and therefore the material acts like its much thicker. In fact the material of this filter is very thin, which may impact the amount of filtration it can do, since we are going to use the material flat.

Remember though we’re not trying for perfection, just something you can use with some degree of confidence it will offer better protection than nothing.

Along with the filter you are going to want to buy a couple of women’s tights.


They had two colors where I bought these, white and a navy blue. Get some in size extra large or double extra large. Get several pair while you can. These ran me $8US.

Pull them out cut the legs off just above the crotch, so you end up with something like this.

tights cut

The elastic waist band is at the top of the picture.

That’s a completed filter to the left. I actually took the filter apart and made the filters first but I would probably cut the tights first instead and get them out of the way. Put the tights to the side for later and throw away the legs.

Ok, here’s a short tool list you’ll need; scissors, a box knife, a black market, some way to measure (tape or ruler) and a roll of electrical tape.

Begin by cutting open the furnace filter to remove the filter material itself.


The material tears easy but the only place its critical is on the front and back, that is on the ends of the pleats. The box top and bottom, and sides will be cut back some.


Now they used quite a bit of the glue on the side panels, too much to bother with trying to peal the filter material off it so go ahead and cut the filter material and the cardboard off the main part. You should end up with something like this.


Now, cut one of the V’s off.


This is where having a 25″ wide filter was fortunate. Seems like a good width of a filter is about 8″, so trim off the filter material on each end which is not covered by the wire mesh, then divide that length in three (about 7.5″) and cut it. This will give us a filter that is two layers of filter material.

A point about the wire mesh: The videos I found online that use this material, the makers remove the mesh. I tried and it looks like it does too much damage to the filter material, so I didn’t.

Also, ideally you would want the wire mesh on the inside of the fold but in this case, the furnace has twelve double sections, which will give 36 mask filters. I didn’t want to try and refold the wire mesh so that it was on the inside because I worried it might break it and produce a sharp point.

There are sharp points though on the other three sides, so I took a length of electrical tape and covered those sides. You can see that in the picture.

It may be that my tape is too old, it didn’t like to stick well. You may want to try other types of tape. All its there for is to protect against sharp points.

There you can see the finished filter elements.

Now lets put the two together into a functional mask.

(yes, I’ve cut my hair.)

First thing is to take the tights and turn them inside out. Pull it over your head, with the waist band at the top.

(sorry this picture is a bit blurry)


Settle it so the elastic band is on your nose, then take one of the filter elements and place it on the mask with the fold at the top.

(it should be a bit higher but don’t worry, it settles once you cover it.)


Take the lower part of the tights, and pull it up and over the filter element.


Then pull the excess up and tuck it under the elastic waist band, pulling it up until the filter element rests at the top of the mask.


Tuck the other material of the tights around your head and into the back and pull out any folds in the front to maximize airflow.

I forgot to take my goggles up with me for the photos.

Now, yes there are some air gaps around the top and bottom. The ones at top should go away once you put your goggles on.

Surprisingly, its pretty easy to breath through. I don’t know if that means I’m not getting much protection or what.

To remove the mask, first unroll the outer layer of the cloth. I would roll it down, rather than push it onto my neck, since the outer layer is contaminated from droplets.

Once the filter element is exposed, remove it and dispose of it. I wouldn’t reuse these unless you were tight on money, though you could heat disinfect as long as you removed the tap.

With the filter element removed, roll the mask up so the outer layer was inside the inner layer, then pull it over your head. That way you shouldn’t contaminate your face.

Wash the fabric layer or chemically disinfect it.

Ok, that’s 36 masks for about $36-40US ($20 for the filter elements and $16 for two pair of tights), or about $1 a mask. Though you could make more filter elements for about 60 cents each after that.

Feel free to change or modify this as needed. And if anyone is good at making videos, please make on of this and put it on Youtube to share.


  • Fri, Mar 20, 2020 - 08:10pm



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    Covid19 – DIY Mask Tutorial

Thank you so much for this. I am extremely grateful for all your posts, and especially this one! I look for your posts on each topic!


  • Sat, Mar 21, 2020 - 09:09am



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    DIY Mask Tutorial – Concern About Filter Material

In comments on another forum (FB DIY Masks), concerns were raised about the filter material, especially whether it is fiberglass.

First, I don’t know. The manufacturer says its a “special formulated material”.

I’ve looked around about fiberglass and filters and the best I’ve been able to tell is that fiberglass filters are typically used in cheaper older filters, the kind that are flat. The newer larger pleated filters are usually a treated paper composite.

Also, this design doesn’t have your skin against the filter, but a cloth layer between it and you. Though the knit size is pretty large.

Bottom line, its a question of filter efficiency versus health risks on short term exposure.

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