larger transport aircraft. Many aircraft have a combination of  both systems that may be augmented by portable equipment. In its simplest form, a continuous-flow oxygen system allows  oxygen to exit the storage tank through a valve and passes it through a regulator/reducer attached to the top of the tank.  The flow of high-pressure oxygen passes through a section of  the regulator that reduces the pressure of the oxygen, which  is then fed into a hose attached to a mask worn by the user.  Once the valve is opened, the flow of oxygen is continuous.  Even when the user is exhaling, or when the mask is not in  use, a preset flow of oxygen continues until the tank valve  is closed. On some systems, fine adjustment to the flow can  be made with an adjustable flow indicator that is installed in  the hose in line to the mask. A portable oxygen setup for a  light aircraft exemplifies this type of continuous-flow system  and is shown in  Figure 16-11. Continuous-Flow Systems A more sophisticated continuous-flow oxygen system uses  a regulator that is adjustable to provide varying amounts of  oxygen flow to match increasing need as altitude increases.  These regulators can be manual or automatic in design.  Manual continuous-flow regulators are adjusted by the crew  as altitude changes. Automatic continuous-flow regulators  have a built in aneroid. As the aneroid expands with altitude, a  mechanism allows more oxygen to flow though the regulator  to the users. [ Figure 16-12] Many continuous-flow systems include a fixed location for  the oxygen cylinders with permanent delivery plumbing  installed to all passenger and crew stations in the cabin.  In large aircraft, separate storage cylinders for crew and  passengers are typical. Fully integrated oxygen systems  usually have separate, remotely mounted components to  reduce pressure and regulate flow. A pressure relief valve  is also typically installed in the system, as is some sort of  filter and a gauge to indicate the amount of oxygen pressure  remaining in the storage cylinder(s).  Figure 16-13  diagrams  the type of continuous-flow system that is found on small to  medium sized aircraft. Built-in continuous-flow gaseous oxygen systems accomplish  a final flow rate to individual user stations through the use of  a calibrated orifice in each mask. Larger diameter orifices are  usually used in crew masks to provide greater flow than that  for passengers. Special oxygen masks provide even greater  1000 1500 500 2000 0 O XYGEN SUPPL Y PRES SURE USE NO OIL Scott $_{ }$A D J U S T T O A L T I U D E O F F 0 5 10 15 20 25 30 O XYGEN SUPPL Y USE NO OIL Scott OPERATION “PRESIDENT” 1. Open supply cylinder valve. 2. Connect Masks. 3. Turn up to flight altitude. 4. No smoking while oxygen is in use. 5. Turn Off before disconnecting masks. Figure 16-11.  A typical portable gaseous oxygen cylinder complete  with valve, pressure gauge, regulator/reducer, hose, adjustable flow  indicator, and rebreather cannula. A padded carrying case/bag can  be strapped to the back of a seat in the cabin to meet certification  and testing specifications. Figure 16-12.   A manual continuous flow oxygen system may have a  regulator that is adjusted by the pilot as altitude varies. By turning  the knob, the left gauge can be made to match the flight altitude thus  increasing and decreasing flow as altitude changes. 16-8