I saw this in video form. The problem is that there are still some common types of masks missing from this study.
For example, I have a mask that has the vortex valve. BUT it is a 5-layer mask, and between it and my mouth and nose is a disposable 3 layer filter. The valve does make it easier to breathe out, but what is breathed out still goes through the 3 layer filter plus one layer of the built-in filters, instead of all 5 layers. I've seen these masks in medical use throughout the Covid pandemic as well. You breath in through 5 filters, and out through 4. And yes, when you take it off after a few hours of use, the smell of the world and any amount of humidity is pretty shocking.
They would be completely correct if I omitted the 3 layer filter, but then the mask is only 2 layers plus the vortex valve with only 1 layer over it, which clearly would be insufficient.
So while it looks exactly like a 3-layer mask with a vortex valve, it isn't one.
For example, I have a mask that has the vortex valve. BUT it is a 5-layer mask, and between it and my mouth and nose is a disposable 3 layer filter. The valve does make it easier to breathe out, but what is breathed out still goes through the 3 layer filter plus one layer of the built-in filters, instead of all 5 layers. I've seen these masks in medical use throughout the Covid pandemic as well. You breath in through 5 filters, and out through 4. And yes, when you take it off after a few hours of use, the smell of the world and any amount of humidity is pretty shocking.
They would be completely correct if I omitted the 3 layer filter, but then the mask is only 2 layers plus the vortex valve with only 1 layer over it, which clearly would be insufficient.
So while it looks exactly like a 3-layer mask with a vortex valve, it isn't one.