Introduction: Face Mask Duckbill With Filter


I'm a physician and a maker. My hospital is currently collecting our used N95 masks for cleaning and possible re-use. I was looking into solutions for if/when we run out. There are quite a few posts for making surgical masks, but I find the 'Duckbill' masks fit my face better than other designs. I hope to continue using 'real' masks, but in a time of shortage, I wanted to at least have something to wear. While homemade masks are not a substitute for true surgical mask or N95, a DIY mask is probably better than nothing. (I make NO promise that this or any mask offers full protection from infectious diseases/ COVID-19.)

UPDATE: Because some individuals with coronavirus lack symptoms, CDC recommends wearing cloth face coverings in public settings where other social distancing measures are difficult to maintain (e.g., grocery stores and pharmacies) especially in areas of significant community-based transmission. (CDC). Please leave N95 respirators for health providers who are in need of PPE. Wash your hands and practice safe social distancing when possible.

If you don't have access to a sewing machine, the CDC has a video to make a very simple mask from a t-shirt and rubber bands.

The CDC changed their recommendation based on newer findings about the high prevalence of asymptomatic carriers. The idea is that by wearing a cloth face mask, you may prevent transmission to others if you are an asymptomatic carrier of coronavirus. In other words a mask may help prevent 'outward' transmission of disease.

As far as 'inward' protection, there is some data that homemade masks *may* help, but they are definitely not a substitute for the real thing (Cambridge Study, Nature, Occ. Env Med, Annals Occ Hygiene, ). For influenza there is some data that N95 mask may not be superior to regular surgical masks in clinical setting (CMAJ, JAMA). So maybe you don't need a N95 (Please stop hoarding unless you are intubating a patient with COVID-19). CDC has gone as far to suggest that even a simple bandana can be used as a 'last resort'. (When N95's are a rare as unicorns, I'd rather have something superior to Chachi's Bandana). To summarize N95 > surgical mask > DIY > Bandana.

I really liked ashevillejm's DIY Cloth Facemask, but it just didn't fit my face very well. You should check out her instructable for ideas and references. Lauren Streicher, MD also has a great video with a different style mask as part of the #millionmaskchallenge. The 'Duckbill' mask just a different style of mask that may or may not work better for your face shape.

I wanted the mask to be reusable, better than a bandana, breathable, and made from materials I could easily acquire. I made the outside from t-shirt material (see Cambridge study above). I made the inside out of cotton/poly blend so it would dry faster. I found filter material that would filter 1 µm particles; I cut out part of a furnace filter. This was a filter made of non-woven polypropylene (not fiberglass). This is definitely not N95 (~0.1 µm) but in theory it may filter water droplets (0.6-1000 µm) (the mechanism for influenza transmission). Please select filter material at your own risk. Read package or contact manufacturer to ensure safety, filter specifications, and durability. Blue shop towels may be a reasonable filter material. Here are some links for other filter materials (NY times).

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  • Cotton fabric (like t-shirt) or cotton/polyester blend (about 11 x 20 inches)
  • Elastic (2 x 9 inches)
  • Filter material (Research and select something you feel is safe and effective) Please don't hoard filters- share with your friends. You only need ~ 10 inch square)
  • Bendable metal (wire, thick aluminum from your carry-out container, I found some aluminum roof flashing)
  • Sewing Machine
  • Soap and water (for washing your hands).

Step 1: Download Pattern and Cut Materials

First of all wash your hands and don't touch your face or nose.

Download PDF below. The pattern makes a 'regular' size Duckbill mask. For a small, subtract about 1/4 inch from outside. I cut 2 black pieces of fabric from a cotton t-shirt for the outside. Then 2 blue pieces of cotton/poly blend from the inside. I then cut 2 pieces of filter (this is optional: I don't have any evidence that this improves function). I found an unused filter in my basement, disassembled it and cut two pieces for the mask. The furnace filter had the advantage of being breathable, washable, and had a sticker that indicated it filtered particles as small as 1 µm. Please do not hoard furnace filters (or toilet paper). Please do your own research to determine if the filter material you select is safe. See comments below for filter material ideas.

Step 2: Sew 3 Layers Together at Top

I placed 3 layers in order: inside (blue), outside (black), filter material and sewed along the top. My sewing skills are limited to 9th grade home economics (Thanks Mrs. Schaffer), so it doesn't look pretty. The 'right' sides of the fabric were facing each other. Do this for the upper and lower portion of the mask.

Step 3: Place Bendable Metal at Top.

Place a strip of bendable metal at the top to allow for nose seal and to minimize fogging of goggles. There are a few options here. I found some aluminum roof flashing that I cut to 1/4 inch x 6 inches. I also was eyeing an old take-out container made of thicker aluminum foil. You could probably use craft wire, or 12 gauge copper electric wire (Romex), or thick twist ties. Flip the fabric around and sew around the strip to keep it in place.

Step 4: Sew the Two Sides Together With Elastic

I found some elastic that was about 1/4 inch and cut two 9 inch strips. You could probably use a light bungee cord, or longer hair tie as well. I placed the upper and lower portion with the outside (black) facing each other. I then placed the elastic at the top and sewed down one side, across the bottom, then up the other side. I stopped just before the top to place the elastic and sew it into place. I trimmed off the extra fabric and was done.

Step 5: Final Mask

I'm sure it could be nicer looking, but it fits my face well with no air leak out the sides and it's pretty breathable. I really like our instant pot for making curry and chili, but I plan on cleaning my mask in it. It's not a real autoclave but I think it's better than rinsing with cold water. (UPDATE: I'm using low setting for 30 minutes. See comments below for alternative cleaning methods and science behind instant pot cleaning). Here is CDC guide for cleaning N95 respirators (Note: this mask is NOT an N95 respirator, so this may not apply. Also, the methods described like hydrogen peroxide vapor or UV light are not really accessible to home user.) Steam looks promising, but cleaning method depends on the materials you use.

Now go wash your hands again.

Please check out Deborahhopetree's alternative PDF below in the comment section. She has real sewing skills and a very detailed guide. Also check out Anyjackie's detailed PDF instructions below in comment section. Both create a more refined mask that looks more professional than my simple design. Gem City Sewn has a fun animal modification for kids.

The second mask I airbrushed a wolf howling at the moon dreaming of a wolf howling at another moon:)