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Comment by munificent | Hacker News Reader

> most of air is actually escaping through the edges of the mask and around the nose.

Why is that a problem? My expectation is that what matters is:

1. Air that you inhale comes through the mask filter. It's not necesarily the case that inhaling and exhaling have symmetric effects. When you exhale, you increase air pressure inside the mask, which pushes it away from your face and opens the seals around the edge. When you inhale, I expect it would seal tighter. You can exhale while wearing a swimming mask and bubbles go everywhere. That doesn't mean the mask isn't otherwise water tight.

2. Aerosol particles from infected people coughing and sneezing get caught by the mask and don't go into your airways.

3. You don't touch your face with your hands.

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Most masks won't filter the virus. N95 can only filter particles greater than 0.3 microns and the corona virus is around 0.16 microns.

The masks are more for stopping behavioral habits for non-infected people like touching your mouth and nose but then you could touch your eyes too...

The masks are more for the infected people who could sneeze and spread the virus particles much further than if blocked by the mask.

>corona virus is around 0.16 microns

But virus particles aren't floating around in the air infecting people, it's spread mostly through respiratory droplets. Not saying that a surgical mask will protect you, but it's not because the virus is too small.

virus particles really are in the air infecting people.

> N95 can only filter particles greater than 0.3 microns and the corona virus is around 0.16 microns.

The virus spreads in much larger drops of fluid.

I'm pretty sure N95 just tells you how many particles are filtered, and the sizes and for which size ranges it is more or less effective depend on the specific piece. Also, droplets are bigger than the naked virus particles and will get caught by the filter.

The masks aren’t fine enough to trap germ particles coming in. There are such masks (n95) but these are more expensive, and require fitting and training to use. The off the shelf masks people are using do nothing for healthy people.

"Well, Technically", 3-ply masks are fine enough to trap germ particles. They consist of a woven:non-woven:woven layer, the non-woven layer blocking nanometer particles. If you look at a n95 mask, it has the same woven:non-woven:woven layer structure.

The problem of 3-ply masks is that 10-25% of the air you inhale leak from the side/nose, bypassing the filter. n95 mask "fixes" the problem by tight(er) fitting, not by additional filtering layers.

https://en.wikipedia.org/wiki/Nonwoven_fabric

> training to use

I keep hearing this but don't understand. What exactly needs training?

Typically it's about putting the straps on correctly and properly adjusting the nose bridge. When you don't put it on properly (i.e. straps above and below the ear, nose bridge properly adjusted) it'll be much less effective.

See https://www.bu.edu/ehs/files/2014/08/N95-Respirators-Trainin...

Common sense

#2 is only true if you get a proper mask and wear it properly. N95 or better. #3 is always true but it is of limited (near zero) value if you aren't also using other methods, namely washing hands.

#1 is not true at all unless you get a proper mask, with a filter, and use it properly. Most people are walking around with a mask they got off the shelf at Walmart that is acting about as effectively as a halloween costume.

N95+ masks are expensive. Currently $20 per mask on Amazon.

You should be fit-tested with an N95 as well. I had a job where it was required yearly and different brands and sizes work better for different people.

> N95+ masks are expensive. Currently $20 per mask on Amazon.

They're not that expensive. That's price gouging, and I'd be worried about them being counterfeit. I have no way of evaluating their effectiveness at home.

I bought a box of 10 3M N95 valved masks three days ago at Ace Hardware for $24.95.

I bought a box of 3 for $20 yesterday from an eBay seller with a good reputation. There's a chance I've been scammed, but I think lower than on Amazon.

Probably not counterfeit, just automated scalping/drop-shipping. Rampant on Amazon these days.

If there aren't counterfeits yet, they'll be coming.

The cheapest N95 masks are around $3 retail ($6 for a pack of 2).

The masks are going for $60+ per mask on eBay right now. And virtually impossible to find on store shelves.

> Aerosol particles from infected people coughing and sneezing get caught by the mask and don't go into your airways

Even if the masks were capable of filtering out the virus, the above wouldn't matter. If the virus hits your eyes or tear ducts you've got it. This is why wearing a mask protects others but not yourself.

Is that a problem? Yes... like I said and shown in my experiment that you can repeat yourself, most masks are like toys, not air sealed or fitted properly and a lot of air gets through the sides, doesn't matter if you breathe in or out, gaps are still there (you will notice cold air entering on the side of the mask when you breathe in, especially if you worn the mask for a while and it gets a little soggy).

Of course, don't get me wrong.. they do work to a degree if fitted properly with the right grade of filtet, but the problem that people are putting too much faith in these things, especially the ones you buy from the combinis..

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