It is a personal protective equipment designed for handling hazardous chemical accidents, protecting the safety of personnel's face and respiratory tract. 2. (1) Protection time: The protection time against mustard gas shall not be less than 360 minutes. (2) Inhalation resistance: not greater than 186Pa under a constant airflow of 30L/min. (3) Exhalation resistance: not greater than 300Pa under a constant airflow of 160L/min. (4) Field of view: The total field of view should not be less than 70%; The binocular field of view shall not be less