Not sure of the exact purpose of the previous post showing an exhalation valve on a mask.
Here's a cropped screen-grab from a PDF of 3M's Cool Flow Valve.
It shows its function and purpose.
As there's obviously some of the exhaled air being expelled through the valve without being filtered, and directed downward and to the side,
it would be very interesting to see one of those videos where it shows the path of someone's breath, especially during coughing and especially
comparing this type of mask (with a valve) and say, a thin cloth layer of a bandana.
