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Comment by XorNot | Hacker News Reader

It's quite likely that in all the scenarios a mask may have a useful effect, N95 or better is the only time it works.

For medical professionals in close contact with patients and dealing with airborne-protocol pathogens (which is what a droplet-mediated pathogens like SARS2 becomes classed as once patients are coughing and being intubated) then a bad mask is quite probably worse then no mask (this has precedent: ineffective masks obstruct breathing, which makes you take deeper breaths and draw more particles in deeper in your lungs - it's a big problem when dealing with fine dusts in construction).

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> It’s quite likely that in all the scenarios a mask may have a useful effect, N95 or better is the only time it works.

You’re saying you think anything less than an N95 has 0 effectiveness. Why do you believe this is likely? Are you aware of the data that says otherwise?

https://news.ycombinator.com/item?id=22655436

https://www.researchgate.net/publication/258525804_Testing_t...

N95 Respirators vs Medical Masks for Preventing Influenza Among Health Care Personnel: A Randomized Clinical Trial

https://jamanetwork.com/journals/jama/fullarticle/2749214

“As worn by health care personnel in this trial, use of N95 respirators, compared with medical masks, in the outpatient setting resulted in no significant difference in the rates of laboratory-confirmed influenza.”

To be clear, this trail was for outpatient care — not necessarily applicable to shoving tubes down throats, but probably applicable to people walking down the street.

That quote is saying that N95 masks are no better than medical masks, not that medical masks have 0 effectiveness.

The data from the Davies paper is not very convincing. The home made solutions offered significantly less protection and and had major problems with fit. Even their conclusions were — it’s better than nothing, but not a proper substitute.

> However, these masks would provide the wearers little protection from microorgan- isms from others persons who are infected with respiratory diseases. As a result, we would not recommend the use of homemade face masks as a method of reducing transmission of infection from aerosols.

Better than nothing is the whole point. N95 masks are not a substitute for avoiding exposure in the first place, but nobody’s saying N95 masks are ineffective because of that fact.

The recommendation here is assuming you have access to something better. If you have no access to something better, a homemade mask is better than no mask at all, until you can get something better. As others have pointed out here, it’s rather odd to suggest we should scoff at this imperfect solution, when there are no perfect solutions short of 100% full and complete quarantine, which is completely unrealistic.

This is about Influenza but I doubt it’s that different from Corona: https://pubmed.ncbi.nlm.nih.gov/20497389/

Are you a doctor? Can you explain why a study about influenza would apply to SARS-CoV-2? Or is your doubt baseless speculation?

SARS-CoV-2 is a spheroid with a diameter of about 120 nm.

There's a lot of variation in influenza viruses, but most are spheroids or ellipsoids with a diameter from 80-120 mm.

For simple mechanical filtering, such as with a mask, they are going to behave pretty similar.

It's highly likely that even basic surgical masks have some impact. A fit-tested N95 is the gold standard, but the widespread use of surgical masks in Asia during the SARS epidemic does seem to have had an impact.

https://wwwnc.cdc.gov/eid/article/10/2/03-0730_article

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