Your comment assumes the entire purpose of a (nearly) sealed mask is to protect the wearer from incoming droplets or particles. I don't understand where this ignorance comes from; it's been widely known and repeated for some time that masks do much more to protect others from infection from the wearer. There's only a small amount of protection for the wearer from infection from others.

An inhalation valve preserves the mask's primary purpose by closing off during exhalation. It gives up a small amount of protection for the wearer, but obviously a lot of people aren't interested in that anyway and refuse to wear masks. With an inhalation valve they could at least protect others.

> Your comment assumes the entire purpose of a (nearly) sealed mask is to protect the wearer from incoming droplets or particles

It doesn’t just assume it. It’s the whole point of the masks.

If your aim is just to prevent making people sick, a surgical mask is just fine (exhibit A, normal doctors).

If your aim is to prevent getting sick yourself, a N95 respirator is a better choice (exhibit B, doctors treating COVID patients).

An inhalation valve does less to protect other people, because the expelled air still has to go somewhere, and will just blow out of the sides of the mask. It could theoretically go through the mask material if it was thin enough, but there’s probably too much pressure inside and it’ll burst out the sides.

That in reverse is the whole idea for masks with an exhalation valve. Breathing in creates negative pressure inside the mask, so air gets pulled inside through the mask. When breathing out the valve opens and releases the extra pressure without blowing out the sides (not really a problem per-se, but would compromise your protection).

> An inhalation valve does less to protect other people, because the expelled air still has to go somewhere, and will just blow out of the sides of the mask. It could theoretically go through the mask material if it was thin enough, but there’s probably too much pressure inside and it’ll burst out the sides

No, an inhalation valve makes 0.0% difference here. Here's a simple mental exercise to understand better. Imagine two people side by side. They are wearing identical masks, except one has an inhalation valve. They breathe in, pause, breathe out. In your mind, freeze the frame at the pause between breathing in and breathing out. At that moment, what's the difference between the two? Nothing. Now watch them breathe out. What's the difference? Still nothing.

Where is this coming from that only a small amount of protection is provided to wearer. For a while I kept on posting studies showing the effectiveness of masks in protection infection by wearer, but it's hopeless - somehow public health authorities have gotten everything so muddled in folks minds.

You answered your own question.

> Where is this coming from that only a small amount of protection is provided to wearer [...] public health authorities

I clicked the HN link to your comments. I couldn't quickly find studies, just a mention of Korea having success with KN94 masks. I think it's safe to repost them now without being repetitive.