They have also followed DL in not allowing masks with valves. I saw a fair number of N/K95 masks with exhalation valves on my last flight. i also saw a guy in a hazmat suit and a full-on gas mask. From the look of him, he would not have taken kindly to being told he could not wear it. I wouldn’t relish being the FA who had to tell him he couldn’t wear his gas mask. It would not have ended well.
Unacceptable face coverings: - Face coverings with direct exhaust valves.
- Face coverings that do not cover a guest's nose and mouth.
- Face shields without masks.