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Comment by melling | Hacker News Reader

I saw a comparison yesterday that claimed with a cloth mask, being in the same room with someone for 30 minutes was enough to catch Covid.

A surgical mask provided an hour of protection.

With an N95, you would need to be in the room for 25 hours.

I believe that was with both people wearing a mask

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I think that stat came from a chart in this article https://yourlocalepidemiologist.substack.com/p/a-quick-note-...

Also this one: https://www.axios.com/n95-mask-protection-covid-958039c9-07f...

I wish they included KN95s for comparison... I prefer them because they're easier to take on and off, and the seal seems reasonable to me (breathing in/out causes the mask to deform, so it's clearly filtering some air)

Aren’t KN95s just N95s with the Chinese standards (vs US standards) but should technically work for the same particle sizes?

GP is probably referring to KF94, the Korean standard. Their form factor is somewhere between a surgical mask or an industrial / medical N95. They are quite popular, here in HK, with people who want to protect their makeup.

Example: https://www.amazon.com/KF94-Protective-Individually-Packaged...

Technically yes, but US standards require a headstrap... which is generally tighter in my experience. I'm wondering if the ear loops reduce efficacy significantly (assuming fit is proper otherwise).

There’s a 5x5 or so graphic floating around of how many hours are safe in different masking situations. While I agree with the relative arrangement, there’s a risk of misinterpretation.

Early in the pandemic some claimed their interactions are short so They can wear no/crappy masks, overlooking that it’s a police officer and their entire day is made up of short interactions…

You can't really give a time like that. People with detectable levels of covid might have anywhere between 100 and 10^14 viral copies/cc in fluid samples taken from them depending on their immune system and stage of progression. Infectiousness is probably proportional to that viral load. How much fluid escapes a person into the air also varies by a few orders of magnitude depending on whether they're sitting quietly enjoying a movie all the way to singing loudly.

You can if it's an average and you're not being overly literal about it. Don't break out a stopwatch and assume you're safe if you run out of the room before the average time is up.

It's not a matter of differences you need a stopwatch for, it's that the times plausibly vary between a second and years.

Interesting intuitive point of view. Too bad there's no evidence for any of that

The infographic is based on ACGIH's Pandemic Response Task Force[1]. The list of references for respirator/mask information is available on their site[2]. I can't speak to the veracity of the evidence provided, but there is evidence.

[1]: https://www.acgih.org/covid19/ [2]: https://www.acgih.org/covid19-references/#resp

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