It seems like the "Pay Day 2" masks slowly kill the person that wears them. It will drain your blood and cause either death or serious damage to you character after an uncertain amount of time.
Tested it with one mask, possible that is also happens with gas masks, since I played at night with full gamma settings and at the next day, when I turned them down again, I was on almost zero blood. (i think is was zero, it was at least really greyish)
Thanks for the game,
greetings from Germany