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Comment by chrisco255 | Hacker News Reader

No, I believe I read that the typical N95 masks that people use is basically useless against this virus, because it's very, very tiny and can sail right through a mask. It still might reduce your exposure and is probably better than nothing, but I believe only a gas mask would totally protect you.

"...there's no evidence inexpensive surgical masks can protect against flu virus particles small enough to be inhaled into the lower respiratory tract or the lungs"

http://www.digitaljournal.com/life/health/do-face-masks-help...

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N95 masks (and other types of HEPA filters) actually perform better on smaller particles.

A very common misconception is that HEPA filters only filter particles larger than 0.3 microns. In fact there's multiple different filtration mechanisms at play, with interception and impaction working better for larger particles, and diffusion being more effective for smaller particles. HEPA filters are rated for their effectiveness at 0.3 microns because that size is the size where the combination of mechanisms operate worst: smaller and larger particles are filtered even more effectively.

https://en.wikipedia.org/wiki/HEPA#Mechanism

Your own cite says that surgical masks are ineffective but properly fitted N95 masks can be effective. I believe that they filter droplets well, e.g. from sneezing.

https://www.asahq.org/about-asa/governance-and-committees/as...

I think they're better than nothing but as someone else mentioned the virus is 0.1 to 0.3 microns and the N95 only filters 95% of particles 3 microns or larger.

I haven't seen conclusive evidence that they're better than nothing.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4868605/

Here you go

This study only finds that N95 are not more effective than surgical masks. It does not measure the effectiveness of surgical masks vs nothing. Did you actually read the study before posting a link to it?

It's worth also noting that this refers to healthcare workers. The considerations are totally different here, because the likelihood that they'll come into close contact with an infected person is pretty close to 100%. The likelihood that a member of the public will in most Asian countries with 20 or so cases and a few tens of million people is more like 0.00001% give or take a couple of orders of magnitude.

See https://www.cdc.gov/coronavirus/2019-ncov/about/transmission...

"Most often, spread from person-to-person happens among close contacts (about 6 feet). Person-to-person spread is thought to occur mainly via respiratory droplets produced when an infected person coughs or sneezes, similar to how influenza and other respiratory pathogens spread."

https://www.cdph.ca.gov/Programs/EPO/Pages/Wildfire%20Pages/...

"An N95 respirator is particularly effective against aerosolized droplets that are invisible to the naked eye."

These droplets can infect you through your eyes as well. Like I said, the mask helps, but no it's not virus proof as Wuhan healthcare workers can attest.

That may well be, but the predominant concern is larger droplets from a cough or sneeze. I don't recall seeing anything speaking of airborne transmission.

Smaller particles get filtered through diffusion based processes: they like landing on surfaces, and the mask is full of surfaces.

The virus isn't going to be airborne naked as an individual thing in the free air - it's going to be in droplets of stuff (from sneezing, coughing, etc).

You're picturing a bare virus flying through the air and getting through a mask.

That's not a plausible route of transmission. The virus would be embedded in a much larger particle of human mucus, and an N95 mask will do a fine job of filtering that out.

Most people are not even wearing N95 masks, they're wearing the much more common and cheaper "surgical masks" that don't form any kind of seal around the outside.

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