delivery system downstream of a converter that is part of the  container assembly.  A small quantity of LOX can be converted to an enormous  amount of gaseous oxygen, resulting in the use of very little  storage space compared to that needed for high-pressure  gaseous oxygen cylinders. However, the difficulty of  handling LOX, and the expense of doing so, has resulted in  the container system used for gaseous oxygen to proliferate  throughout civilian aviation. LOX is used in military aviation  and some medical helicopter applications for patient oxygen. Sodium chlorate has a unique characteristic. When ignited,  it produces oxygen as it burns. This can be filtered and  delivered through a hose to a mask that can be worn and  breathed directly by the user. Solid oxygen candles, as they  are called, are formed chunks of sodium chlorate wrapped  inside insulated stainless-steel housings to control the heat  produced when activated. The chemical oxygen supply is  often ignited by a spring-loaded firing pin that when pulled,  releases a hammer that smashes a cap creating a spark to  light the candle. Electric ignition via a current-induced  hot wire also exists. Once lit, a sodium chlorate oxygen  generator cannot be extinguished. It produces a steady flow  of breathable oxygen until it burns out, typically generating  10–20 minutes of oxygen.  [Figure 16-7] Solid oxygen generators are primarily used as backup oxygen  devices on pressurized aircraft. They are one-third as heavy as  gaseous oxygen systems that use heavy storage tanks for the  same quantity of oxygen available. Sodium chlorate chemical  oxygen generators also have a long shelf life, making them  perfect as a standby form of oxygen. They are inert below 400  °F and can remain stored with little maintenance or inspection  until needed, or until their expiration date is reached. The feature of not extinguishing once lit limits the use of  solid oxygen since it becomes an all-or-nothing source.  The generators must be replaced if used, which can greatly  increase the cost of using them as a source of oxygen for  short periods of time. Moreover, chemical oxygen candles  must be transported with extreme caution and as hazardous  materials. They must be properly packed, and their ignition  devices deactivated.  The molecular sieve method of separating oxygen from the  other gases in air has application in flight, as well as on the  ground. The sieves are relatively light in weight and relieve  the aviator of a need for ground support for the oxygen supply.  Onboard oxygen generating systems on military aircraft pass  bleed air from turbine engines through a sieve that separates  16-5 Figure 16-6.  A spherical liquid oxygen onboard container used  by the military. Figure 16-5.  A portable pulse-type oximeter displays percentage  of oxygen saturation of the blood and heart rate. Pilots can adjust  oxygen supply levels to maintain saturation and avoid hypoxia. below –183 °C or by placing gaseous oxygen under pressure.  A combination of these is accomplished with a Dewar bottle.  This special container is used to store and transport liquid oxygen. It uses an evacuated, double-walled insulation  design to keep the liquid oxygen under pressure at a very low  temperature.  [Figure 16-6]  A controlled amount of oxygen  is allowed to vaporize and is plumbed into a gaseous oxygen  Chemical or Solid Oxygen  Onboard Oxygen Generating Systems (OBOGS)