sal wrote: ↑
Sun Oct 11, 2020 2:36 pm
Masks are becoming a bit of an issue as to their function. I've recently hear that the visors that re being used are not effective. The plexiglass pieces used for separation are also not effective. Two layer masks are not effective. Three layers minimum. Most masks with three or more layers are effective for not spreading, but only N95 maks re effective for keeping it out.
I'm watching many wearing two layer masks or bandanas that supposedly don't work to stop spreading.
It's getting to where finding a definitive truth is getting harder and harder. Who can you trust to actually know?
A sad state we find ourselves in these days not knowing who to trust and questioning the information and guidance put out by the people and organizations trying to protect others and communities. There are two different functions of masks... 1.) to protect the person wearing the mask (i.e., personal protective equipment, or PPE), and 2.) to prevent the person who's wearing the mask from spreading their respiratory droplets (and possibly COVID) to other people.
Healthcare providers wear medical grade masks as PPE to protect themselves when caring for patients. Medical grade surgical masks and N95 masks are what are recommended/used by healthcare professionals.
For the general public, businesses, etc. the recommendations is for non-medical "cloth face coverings" to prevent spread of a person's respiratory droplets to other people. There are both anecdotal reports of cloth face coverings/masks being used and effective for this person (see report of two hair stylists who had COVID-19 and worked for a combined 17 days while infectious, exposing 139 clients, but people wore cloth face coverings, and nobody came down with COVID-19: https://www.cdc.gov/mmwr/volumes/69/wr/mm6928e2.htm
), and also more experimental evidence looking at the ability of masks made with different layers and different materials to prevent droplet dispersion: https://advances.sciencemag.org/content/6/36/eabd3083
(see figure 3, which is probably most interesting). Two layers are better than one layer... three layers probably better than two layers. There are differences in materials due to filtration efficacy. Most of the non-medical masks for sale to the general public currently (Amazon, Home Depot, big-box stores, etc.) are multiple layers.