Face Masks and Breathing

[Ray]

Debbie had been making masks with three layers but plans to try two layers.

Ray, what are your thoughts?

My immediate thought is that Olgry will probably be our resident expert on this....

My wife has been making beautiful masks with space for a filter. Jo-Ann Fabrics has had a hard time keeping her stocked.

Like any filter, higher resistance suggests higher efficiency, and might be desirable. Debbie might want to keep a few of the 3-layered masks around for this winter's Flu/SARS-CoV-2 "perfect storm," which will probably come as a Christmas present to the country....

Reminder:
A mask may not protect the wearer, but it may keep the wearer from spreading the virus to others. - CDC

For more about wearing cloth masksClick here.

The CDC guidelines distinguish masks from "filtering facepiece respirators" (like N95). In making their recommendations, the CDC considers a mask to be cloth or the equivalent of a surgical mask.

For a list of the difference between simple surgical or cloth masks and NIOSH N95 (or equivalent Chinese KN95) masks/"respirators" see below or Click here

At this point, it is all about reducing risk as much as possible. We wear masks because we respect each other (most of the time) and try to keep our germ-laden respiratory droplets to ourselves. Unimpeded, and depending on airflow, most of the big droplets that escape fall over 10-15 min. to surfaces at a range of from 2 meters (the 6 foot rule) to 4 meters. Those surfaces are now contaminated, and if they are plastic or steel, sometimes for days.

The problem is that some droplets become aerosolized (<1 micron) and can linger infectiously in stagnant air (indoors) for hours. So in the hospital, I wear an N95 mask that only lets through 5% of the 300 nm particles (but more of the smaller aerosols). You won't hear much from the CDC or WHO about aerosolization because there are not enough N95 masks to go around. But, even a cloth mask significantly reduces aerosol production, so we are back to wearing masks to protect others.

In the end, one of the biggest differences between masks I wear at work and 2-3 layer cloth masks are fit. Most of us have had to wear masks for some dusty task or another around the house or work, so we know fit is everything. The sides need to match and ride the shape of the face sufficiently that we can't inhale through the gaps. A good nose piece is essential.

All that said, I appreciated Darrell's comments that recognize we might need to practice comfortable breathing with our masks - no matter what type we use. The more we wear them, the more comfortable we'll be. Spend a day wearing a mask, practice not touching the mask, practice breathing, learn not to sneeze.... A prolonged period will also ensure you have a comfortable fit and are not allergic to any of the components.

Here's a pretty good, recent review from the Journal Science. If you can't get through on this link and want a copy for educational purposes only, let me know, and I will send you a PDF version.
Reducing transmission of SARS-CoV-2 Kimberly A. Prather, Chia C. Wang, Robert T. Schooley