We were to continue building on the house in early April 2020. Our travel plans were of course interrupted. I had 3 weeks of vacation so started keeping busy working on farm projects. Then the CDC said we really do need face masks. While the cloth ones that I had seen did look cute, I knew from my military chemical warfare practice experiences that we needed something better. Also, our middle son had used every woodworking dusk mask that I owned while working on projects in my shop. I did have one very dusty one left but that was it.
So then I found an article where the Medical Engineering department at Texas A&M had come up with an N95 equivalent mask design using a filter element made from air conditioner filters. Here it is:
Off I went to the Home Depot to secure the AC filters before the hoarders figured this out. One thing about getting the filters is that Home Depot uses a different rating system than everybody else. So the Home Depot FPR rating of 10 is equivalent to the standard MERV 13 rating. You want at least that rating. If you can find a MERV 16 filter then that is best. One 20 x 25 inch filter will make 5 masks using 4 layers of material (for MERV 13 you will use 4 layers, MERV 16 one layer). Once home I started harvesting the material. The article was talking about cutting the wires and other things, I found it just as easy to peel the cardboard and wires with my fingers without cutting anything. After about 20 minutes I had this:
I made one mask using the directions from Texas A&M. They were using a stapler to hold everything together. I found that my normal household stapler wouldn’t make it all the way through the material sometimes. I did finish that mask and found that it did seem to fit very well. I didn’t think it would last long though, so the next day I got out my sewing machine and made another using some slightly different dimensions.
You going to need four 9″x6″ sheets of at least MERV 13 material, one 9″x6″ sheet of a sheer fabric, one 10″x8.5″ sheet of sheer fabric, one metal nose piece, and two 36″ long pieces of tie string. When cutting the filter material cut it so the pleats are parallel to the long (9″) axis of the rectangles. For the sheer fabric a light fabric like a handkerchief or worn out T shirt will work. First take the bigger piece of cloth and put on table. Then the four layers of filter material, then the smaller piece of cloth. It should look like this:
Next fold the 3 sides with the 1/2 inch margin over the rest of the stack and sew through all the layers.
The metal nosepiece needs to be about 1/4″ wide and 5″ long. I tried folding some aluminium foil to make one but it was not strong enough. I ended up cutting some aluminum roofing flashing into a 1/2″ x 5″ piece. I then folded it over one time and hammered it flat. I used superglue to secure the nosepiece to the top of the smaller cloth piece like so:
Then I took the 2″ margin of the larger cloth, folded it over the stack, and sewed around nose piece to secure it.
Next fold the entire stack in half centered on the nosepiece. Then along the bottom sew through the stack with the following pattern. You might have to take the foot off your machine for the rest of the steps as the material is getting thick at this point.
Fold from the inside of the mask by the nosepiece around the cords and sew to secure. I found it was better to not sew through the cords so that they could slide through the pocket.
Now you’re done! I know it looks goofy but it is very effective.
