I'm not a medical pro. My experience with masks has been for dust and fumes. The valves emit drips on rubber respirators. I assume the valves on paper N95 masks exhaust your breath and any virus you may have.
I was surprised to see that the CDC says N95 Masks with Valves are OK for medical workers. Since you can have Covid-19 without symptoms this surprised me.
This is from the CDC:---
An N95 respirator with an exhalation valve does provide the same level of protection to the wearer as one that does not have a valve. The presence of an exhalation valve reduces exhalation resistance, which makes it easier to breathe (exhale). Some users feel that a respirator with an exhalation valve keeps the face cooler and reduces moisture build up inside the facepiece. However, respirators with exhalation valves should not be used in situations where a sterile field must be maintained (e.g., during an invasive procedure in an operating or procedure room) because the exhalation valve allows unfiltered exhaled air to escape into the sterile field.----
Am I missing something?