... , exhalation valve, and drinking device are designed as one body. The exhalation valve is easy to remove so that ... the left lower part of the faceblank respectively with one of three numbers: 1(small), 2(medium) or ... leakage on the mask, a mask, which is one size smaller, should be instead of it.3.3 ... canteen. When the wearer needs to drink water, one hand should keep the mask steadily, the middle finger ...