The wearer must be clean-shaven to wear respirators that seal tightly to the face. Beard, stubble or long mustaches may 佩戴防毒口罩之前请首先确认已经剃干净胡须，从而使防毒口罩与面颊紧密贴合。胡须或没有剃干净的胡茬会导致防毒口罩与面部之间留下很大缝隙。