Monday, August 17, 2020

Face Mask Science 3, August 2020 edition

Do you have face mask confusion?  Do conflicting headlines give you headaches?

I sort of feel like I've read enough to know that I should wear one whenever I am indoors in any place that is not my own home.  I should also carry one whenever I am outdoors and be ready to put it on whenever anyone is nearby.

There is no way to reduce risk 100%, but we can reduce it to pretty low by:

  • Social distancing in the sense that we minimize going out where we could encounter other people--especially in poorly-ventilated indoor places
  • Social distancing in the sense of putting as much space (and air) between you and others outside your household when you do go out
  • Universal mask wearing, especially indoors
  • Good hygiene (cleaning surfaces, washing hands, not touching face, etc)

The even better news is emerging evidence from multiple countries and situations/studies that show that universal masking reduces the severity of Covid-19 illness if you do catch it. The idea is that viral load matters.  The higher the viral load, the more severe the illness. 

  • Try to avoid situations where you can be exposed to the virus.  
  • Assume that everyone is contagious (even though usually, it's less than 1%, often much less than 1% of the population.) 
  • Then minimize your exposure.

The shaped 2-layer cotton masks I sew are fine for essential shopping trips and the occasional doctor visit.  The problem is finding masks that are comfortable enough to wear when being active (walking, biking, gardening.)

I made some gaiter-style masks with poly/lycra knit sewn into a tube, with a ponytail port at each end.  They were comfortable enough to wear for exercise, but a recent article said that gaiter masks might be worse than nothing.  That made no sense.

Fortunately, Professor Brent Stephens wrote 6000 words about what we know and don't know about masks, different materials, and Covid-19. What kind of mask should I be wearing to protect against COVID-19?

He has some thoughts on Gaiter-Gate, which I need not replicate here. Go read his analysis on why that gaiter measurement (with no control) is highly suspect.  Other scientists pointed out that the measurement that showed a "fleece gaiter" was worse than a bare face at containing droplets might have been measuring fleece fiber shedding instead of droplets.

Professor Linsey Marr wrote how she runs with a gaiter and doubles it up when anyone is nearby.  She posted a presentation on the blocking efficiency of neck gaiters.  The bottom line is that the thin kind that I sew blocks 50-90% of particle sizes that matter when worn in a single layer.  When doubled over, they block 90% over the entire range.

Lab setup:

The data:

The airbrush and spray bottle produce large droplets that, in the absence of a mask or neck gaiter, land on glass slides attached to the opposite manikin’s face. When either neck gaiter was affixed to the spraying manikin, no droplets were observed on the opposite manikin. Thus, the neck gaiters are 100% efficient at blocking these droplets from reaching the opposite manikin’s face.

I know that I sound like a broken record, but the best mask is the one that you will keep on.

Anyway, I am heartened from all of this advice from scientific experts.  It makes Covid-19 less scary.  I have enough to worry about with the elections and the census. 

In other news, this pandemic has made me read up on indoor ventilation and reminded me of sick building syndrome.  I was the canary in the goldmine for that and remember being treated like I was crazy.  One doctor even told me that he ordinarily sends patients who present with my symptoms to psychiatrists but he didn't think that was my problem; after all, I don't dislike technology and chemicals if I decided to major in it.  I'm assembling a blog post with very interesting things I learned.  I even ordered test equipment for my home. 

The mask series.