It can be equipped 1/2/3canisters with different functions according to diverse situations. Specifications: 1. Time of gas defence:depending on the canister. 2. Exhalation resistance: ≯98 pa at 30L/min. 3. Visual field: total ≮ 75°, binocular visual field ≮60°. Below visual field≮40° 4. Oil mist penetration coefficient: ≯0.005 at 30L/min. 5. Leakage of mask: ≯0.005% 6. Storage life:5 years in condition that canister shall be stored stated as follows. 7. Raw material of mask body: silicone/natural rubber 8. Raw material of straps/headpieces(5/6 pieces): silicone/natural rubber Size: Width 19+-1mm Thickness:1mm 9. Raw material of lens: Polycarbonate