Quote:
Originally Posted by cromag
This is true for the inhalation, but not for exhalation, which is directed and relatively forceful. That's why you can put out a birthday candle by blowing, but not by inhaling. Getting a proper fit isn't too difficult.
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LOL, you need to get a physics book and read it. Also, there seem to be a lot of us here who would argue that your "easy to get a good fit" part is not true for everyone.
It doesn't matter if we are discussing pneumatic pressure or fluid pressure, both will take the path of least resistance. If you have no mask on, then expect the path to be outwards from your face. If you have a mask on that can block or impede the flow, then expect the path to be toward the areas of the mask which have the least resistance to the flow. In other words, the path will tend to be around the edges of the mask that seal the least and thus have the least resistance to the flow. Even that video you posted clearly shows flow up to the eyes. The better the mask, the less flow through the mask material and the more flow near the edges of the mask where it doesn't seal well. A crappy mask is another story, of course, but even with a crappy mask there will be flow around the edges.