Filtration Mask

Under normal circumstances, when treating patients with infectious diseases known to have airborne spread (measles, tuberculosis, now SARS-CoV-2), we isolate patients in negative pressure rooms with strict personal protective equipment (PPE) rules.  In New York City, we have run out of space and PPE.  COVID-19 patients are in regular ER rooms, with no walls, just curtains, sitting on chairs in the hallways.  Masks and gowns are being rationed.  Anecdotally, doctors on the front lines are given one N95 mask per week to reuse.  The CDC recommends that people use bandanas instead of disposable masks.  This reality is horrifying and this is just the beginning.

Under normal circumstances, cloths masks are not recommended.  Cloth masks have been shown to be worse than disposable masks.  There has not been a study, to my knowledge, comparing cloths masks with no masks, which is the situation many doctors and nurses are finding themselves in right now.

Dato et al (2006) describe a reusable, washable filtration face mask that may be constructed using white cotton t-shirts.  Below are the steps to making your own mask.  For one face mask, I used two XL 100% cotton t-shirts, scissors, ruler, needle, and thread.

(1) Pre-wash t-shirts in hot water and dry on high heat.  If you do not have a washer dryer, you may boil the t-shirts for 10 minutes and air dry overnight.


(2) Measure and cut a rectangle that is 37 cm x 72 cm.


(3) Create the filter with 23×23 cm squares — you will need 4 that are straight grain and 4 that are cross grain.


(4) Going back to your large rectangle – mark the approximate center either by folding it in half or measuring 36 cm from the sides.  Now we will mark where your 23 cm squares will go to create the filter.  Measure 11.5 cm from either side of the center.

(5) Your mask will have three “ties” to be used to secure the mask around your head.  To create these, measure 15 cm from bottom and 8 cm above this.  Cut horizontally as pictured.


(6) Layer your 23 x 23 cm squares — with alternating cross grain and straight grain squares: two cross grain, two straight grain,  two cross grain, and two straight grain.  Secure each of these at the corner with several stitches at the “x” using needle and thread or a sewing machine when available.


(7). Put your mask on.  Roll down the top of the material to cover the top of the inner layers.  Based on diagram you may put mask on over your face.

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Source: Dato VM, Hostler D, Hahn ME. Simple respiratory mask. Emerging Infect Dis. 2006;12(6):1033-4. PMID 16752475.