Misleading Media Reports That CoV-2 Immunity Quickly Disappears
Good Progress On The Vaccine Front

Using And Re-Using N95 Face Masks

In these pages, I previously talked about the basics of face masks, and how their wide spread use might have the same, if temporary, effect of attaining herd immunity. Keep in mind that your typical cloth mask or bandana mostly protects others from oral spray from an infected wearer. They are not very effective at protecting the wearer since most of the inhaled air comes in from the edges and is not well filtered by the mask. In order to protect yourself from airborne virus, you need to wear an N95 respirator mask that is fitted to your face. Early on, the masks were hard to find, but, lately I have seen long shelves of them at hardware stores.

Peter Tsai is the Taiwanese/American who invented the synthetic fabric that make N95 masks effective at filtering 95% of particles in the air. Tsai made the fabric using an electrostatic charging method. Put simply, the mask's filter contains both positive and negative charges. Neutral particles, like bacteria and viruses, gain a charge when they contact the fabric, trapping them before they can pass through the mask.

Tsai was retired for two years when the pandemic struck. Because of the early shortage of N95 masks, he heard that healthcare workers were reusing them, so he went back to work at the University of Tennessee, Knoxville’s Research Foundation to research the best way to sterilize the masks for re-use. He tested a variety of methods: He left the masks out in the sun, put them in the oven, washed them with soap and steamed them. The best method, he found, was keeping the masks in 160-degree dry heat for 30 minutes, which can be done by hanging them in an oven.

But that's not his preferred method. Tsai recommends buying seven N95 masks and rotating them, using a new one each day. After using one mask, he hangs it in an isolated spot and doesn't use it again for seven days, so any pathogen it catches becomes inactive over time. Various environmental studies of the CoV-2 virus find that it survives a few hours to a few days, depending on the surface the virus is on. It seems to have a shorter survival time on cloth and fabric, perhaps due to desiccation of the virus particles caused by the absorptive properties of the material.

While wearing N95 masks will greatly reduce respiratory exposure to the virus, they are not perfect. You can still pick it up from surfaces and you can even be infected by airborne virus through your eyes. Also, the masks can be quite uncomfortable, and if worn for hours at a time, cause bruising and skin irritation where it fits to the face as shown in the selfie below. Also, be aware that extended use of the respirators can lead to reduced oxygen levels in the blood. One report a few weeks ago told of a nurse who passed out after wearing her mask for several hours. Therefore, only wear them when you are in a crowded situation or in a room, like an elevator that has been recently occupied by many people where virus could remain in the air. Do not wear them in your home, car or outside when you are well separated from others.

Finally, remember these recommendations apply only to the N95 respirator masks. They do not apply to regular masks that are not very effective at protecting the wearer. They are much better at protecting others from an infected wearer.



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