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The Type 4 protective mask (Japanese: 防護マスク4型) is the current respirator of the Japan Ground Self-defence forces. 
The type 4 is famous for being used in actual battles for the decontamination of sarin in the subway, terrorist incident case by Aum Shinrikyo. This mask was developed by KOKEN（興研） in 1985. 
The protective mask type 4 (B) is an improved version of the protective mask type 4. The audio transmission part has been changed from a metal part to a plastic part, and the lens part that secures the field of view extends vertically, making it possible to secure a better field of view. A drink tube was also added. In addition, type 4 (B) mask is folded in two from the center in a compact way to improve storage.