MSA AirHawk II Supplied-Air Respirator includes Advantage 4000 medium Hycar rubber facepiece with rubber head harness, 30 min aluminum cylinder and nylon harness with chest strap. Respirator is designed to maintain a positive air pressure inside the facepiece during inhalation and exhalation. Facepiece featuring molded polycarbonate lens has four-point silicone head harness for exceptional head comfort and security. Facepiece has a one-way check valve to avoid exhaled air from entering the mask-mounted regulator. Air mask is lightweight, durable and economical for many industrial IDLH applications. Cylinder operates at a pressure range of 2216 - 4500 psig while shoulder straps have easy-to-release friction buckles to positively retain pull straps.