Agent Containers Fire Prevention 17-21 Figure 17-30.  Components of fire extinguisher container.  Mounting lugs (4) Nut Pressure gauge Bottle Packing ring Cartridge Strainer Contact assembly Gasket Discharge plug (or valve) body Swivel nut Bottle outlet Oxygen system equipment must be kept absolutely free from  traces of oil or grease, since these substances spontaneously  ignite when in contact with oxygen under pressure. Oxygen  servicing cylinders should be clearly marked so they cannot be  mistaken for cylinders containing air or nitrogen, as explosions  have resulted from this error during maintenance operations. Note: The preceding material in this chapter has been largely  of a general nature dealing with the principles involved and  general procedures to be followed. When actually performing  If a cartridge is removed from a discharge valve for any  reason, it should not be used in another discharge valve  assembly, since the distance the contact point protrudes may  vary with each unit. Thus, continuity might not exist if a used  plug that had been indented with a long contact point were  installed in a discharge valve with a shorter contact point. Care must be taken in the replacement of cartridge and  discharge valves. Most new extinguisher containers  are supplied with their cartridge and discharge valve  disassembled. Before installation on the aircraft, the cartridge  must be assembled properly in the discharge valve and the  valve connected to the container, usually by means of a swivel  nut that tightens against a packing ring gasket.  [Figure 17-30]  Leaking fuel, hydraulic, deicing, or lubricating fluids can  be sources of fire in an aircraft. This condition should be  noted, and corrective action taken when inspecting aircraft  systems. Minute pressure leaks of these fluids are particularly  dangerous for they quickly produce an explosive atmospheric  condition. Carefully inspect fuel tank installations for signs  of external leaks. With integral fuel tanks, the external  evidence may occur at some distance from where the fuel  is actually escaping. Many hydraulic fluids are flammable  and should not be permitted to accumulate in the structure.  Sound-proofing and lagging materials may become highly  flammable if soaked with oil of any kind. Any leakage or  spillage of flammable fluid in the vicinity of combustion  heaters is a serious fire risk, particularly if any vapor is drawn  into the heater and passes over the hot combustion chamber. maintenance, always refer to the applicable maintenance  manuals and other related publications pertaining to a  particular aircraft. the electrical leads and discharge line from the plug body,  which can then be removed from the extinguisher container. 