It is widely used in the field of fire-fighting, chemical industry , petroleum industry, shipping, laboratory mines and metallurgy, warehouses, etc.. Protecting fire fight from smoke fumes andtoxic gases. Providing respiratory protection from airborne workplace hazards. The productshas been both inspected and approved by the national quality testing center and the Register of Shipping" CCS" .The new model with smaller size , higher positive pressure , lower respiratory resistance , more convenient for maintenance contains the hand button and bypass assembly. When the switch of the cylinder valve is opened, you must close the air port ( push the hand button inwardly) This product provides user with a qualified air-tight face mask which possess wild mission . The air-supply set provides user with a new model of stable demand valve with the properties of smaller size and lighterweight. The backboard is made of qualified stress material. The cylinder containing high pressure of air possesses a proper safe parameter. The pressure reducing valve assembly provides an alarm, which whistles at certain range of air pressure to warn user to leave the dangerous area in time.