[dragontamer]

So, here's some information I've been seeing about masks.

1. After breathing in a mask for a while, the outside is now "potentially contaminated" with COVID19. Treat the outside of a mask as if it were infected.

Do NOT touch the mask while using it. Do NOT rub your eyes, etc. etc. Do NOT put on the mask backwards. It is recommended to color-code the inside and outside to make it easier to see.

2. There are a ton of discussions about how to disinfect a cloth mask. Kitchen equipment is commonly recommended. Boiling the mask, letting it sit in the oven for some time, etc. etc. You only need to raise the temperature to ~212F or so (boiling) to disinfect. (maybe lower, but boiling is easy because the bubbling water serves as a temperature gauge).

There may be easier chemical treatments, such as bleach when you're washing the cloth mask. But boiling is obviously safe.

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Note that "N95" masks are only 95% effective against viruses (even if you did everything correctly). Homemade masks will probably only reach 70% or maybe as low as 50%. You aren't invulnerable, you just have a layer of protection on.

I think this "home made mask" idea is very good. We need to leave the N95 masks for professionals, because the USA has a mask shortage (and N95 masks are disposable. One-time use).

Home-made masks can be reused through washing.

[hirundo]

> Homemade masks will probably only reach 70% or maybe as low as 50%. You aren't invulnerable, you just have a layer of protection on.

This protection is more than the numbers may seem. See this essay on the benefits of contracting a disease in a smaller dose:

http://www.overcomingbias.com/2020/03/variolation-may-cut-co...

> The most directly relevant data is on SARS and measles, where natural differences in doses were associated with factors of 3 and 14 in death rates, and in smallpox, where in the 1700s low “variolation” doses given on purpose cut death rates by a factor of 10 to 30.

If you can cut the dose by 70%, it gives your immune system more time to ramp up ahead of the virus, which often translates into a more controlled infection with lower level symptoms, if any.

[bmn__]

Do not boil or steam respirator masks. It destroys the material and renders it less effective, sometimes drastically so.

Instead disinfect them with dry heat in an oven or rice cooker. https://news.ycombinator.com/item?id=22680799

[dragontamer]

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3373043/

Perhaps my advice is specific to repurposed T-shirt masks then. But this study boiled the masks before testing and use.

The study was designed for poorer countries without as much infrastructure. Which is why the materials are so simple and the methods crude. But those attributes are very useful for the DIY community.

[gjlawran]

Here is an awesome technical video on using different methods to clean and reuse masks. Deals with Ozone, Alcohol, UV other disinfectants https://www.youtube.com/watch?v=2UdtKssU7po

[pmoriarty]

"Note that "N95" masks are only 95% effective against viruses (even if you did everything correctly)."

There are masks that offer greater protection than N95. Among them are N99, N100, and various others. There's a good article that discusses some of the differences here: [1]

"N95 masks are disposable. One-time use"

Some types of N95 masks are disposable, others are reusable. Also, even the disposable kind could be (and have been) reused. This is, for example, widely done in hospitals where there's a short supply of masks, on the theory that some protection (even if imperfect) is better than no protection.

[1] - https://fastlifehacks.com/n95-vs-ffp/

[cameldrv]

If there is a good seal, N95 will do better than 95% in almost all cases. The 95% is for the maximum penetrating particle size, i.e. the worst case size particle. This is typically about 0.3um. Particles that are larger or smaller than this will be filtered above 95%. If you want to nerd out on filtration theory, https://en.wikipedia.org/wiki/HEPA is a good place to start.