Do masks actually work?
Channel: Orion Lawlor
Date: 2020-07-03

In my garage I built an aerosol testing apparatus to measure whether consumer-grade or 3D printed masks can really stop aerosols.  In my testing, the best masks stop 90% of aerosols, the worst masks stop 10% of aerosols, and a lot depends on how well they fit your face.

DISCLAIMER: I am not a medical doctor, and the numbers in this video were measured by me in my garage--for something this important you need to make your own decisions.  The aerosol capture rates I measured also have error bars of between 10 and 20 percent.  

There is misinformation going around claiming "masks do nothing".  This is incorrect--even the worst masks stop some aerosol (over 10% in my testing), and should stop most larger droplets.

I'm using a 3D printed head with a cast ballistics gelatin face that wears the mask, a worn diaphram pump as my aerosol generator, and an optical particle counter to measure how many aerosol particles make it through the mask.  I use graphite-filled conductive flexible or copper tubing to reduce electrostatic filtering of aerosols inside the apparatus, and painted the 3D printed head with graphite to make it conductive as well.  An Arduino switches between sampling the incoming and outgoing air to determine the mask's real on-face aerosol capture rate.  

Most of this kind of testing tries to determine if the mask will stop contaminated aerosols from reaching your face (healthy person wears the mask), but because of asymptomatic or presymptomatic transmission, it's also important to stop contaminated aerosol from leaving your face too (infected person wears the mask).  For this reason we flowed aerosol out the nose of the test face, and measured aerosol in the environment around the head ("source control").  For non-valve mask designs, with most filters the aerosol capture efficiency is likely to be similar in both directions.

Our work-in-progress technical report is available here:
   https://docs.google.com/document/d/1Q9jaSaZRyKj-hi1BDpFaLHJNcuCx2OrSKFoyBqVJWUo/edit#

My Alaska Micro Mask design can be downloaded for noncommercial use on thingiverse:
  https://www.thingiverse.com/thing:4378894

When I hike in the woods here, I wear a 10mm Glock on my right hip, and a can of bear deterrent on my left hip.  In my 15 years of living here I've never needed to use either one, but every year somebody in Alaska gets torn up or killed, so I keep wearing them.  (In addition to minivan-size bears, we also have packs of wolves here that are each bigger than some lower 48 bears.  Both of them kill and eat half-ton moose, who are a big hazard on their own!)  

When I go shopping, I wear an old (2014?) 3M N95 that I've had for years in my garage.  After shopping, I leave the N95 on my dashboard so the sun's heat and UV help to dry and sanitize it.

During the school year I work for the University of Alaska Fairbanks, and some students and equipment that helped with this project were paid by a small research grant from the Office of Naval Research, but I did this work in my garage on my own time.  Dr. Javier Fochesatto generously loaned the optical particle counter, and provided extensive and ongoing aerosol measuring advice.     Several others provided help and advice, but neither UAF nor ONR have reviewed or approved these results, or this video.