10 20 0 40 50 30 60 psi Pressure regulator Pressure reducer Filter Filter Shutoff valve Charging valve Check valve Charging connection Green blowout disk Oxygen cylinder Pressure gauge Mask outlet Calibrated orifice Mask outlet Calibrated orifice Mask outlet Calibrated orifice Pressure relief valve Adjustable flow indicators Rebreather face mask Rebreather cannula A B 16-9 Figure 16-14.  A rebreather cannula (A) and rebreather bag (B) capture exhaled oxygen to be inhaled on the next breath. This conserves  oxygen by permitting lower flow rates in continuous flow systems. The red and green devices are optional flow indicators that allow the  user to monitor oxygen flow rate. The type shown also contains needle valves for final regulation of the flow rate to each user. Figure 16-13.  Continuous flow oxygen system found on small to medium size aircraft. flow via larger orifices for passengers traveling with medical  conditions requiring full saturation of the blood with oxygen.  Allowing oxygen to continuously flow from the storage  cylinder can be wasteful. Lowest sufficient flow rates can be accomplished through the use of rebreather apparatus.  Oxygen and air that is exhaled still contains usable oxygen.  By capturing this oxygen in a bag, or in a cannula with oxygen  absorbing reservoirs, it can be inhaled with the next breath,  reducing waste.  [Figure 16-14] The passenger section of a continuous-flow oxygen system  may consist of a series of plug-in supply sockets fitted to the  cabin walls adjacent to the passenger seats to which oxygen  masks can be connected. Flow is inhibited until a passenger  manually plugs in. When used as an emergency system in  pressurized aircraft, depressurization automatically triggers  the deployment of oxygen ready continuous-flow masks  at each passenger station. A lanyard attached to the mask  turns on the flow to each mask when it is pulled toward the  passenger for use. The masks are normally stowed overhead in 