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The purpose of the regulator of a flight deck oxygen system is to:

1. decrease oxygen pressure from 1800 PSI (in the bottles) down to about 50-75 PSI (low pressure system)
2. supply 100% oxygen
3. supply diluted oxygen
4. supply oxygen on demand
5. supply oxygen at positive pressure
6. trigger the continuous cabin altitude warning at 10000 ft cabin altitude.

The combination that regroups all of the correct statements is:

  • A
    2, 3, 4, 5
  • B
    1, 3, 4, 6
  • C
    1, 2, 3, 4
  • D
    3, 4, 5, 6

Refer to figure.

Flight Crew oxygen masks are the quick donning type with a mask-mounted regulator.

A mask-mounted regulator supplies a mixture of air and oxygen or pure oxygen, or performs emergency pressure control. With the regulator set to NORMAL, the user breathes a mixture of cabin air and oxygen, the content of which varies with cabin altitude (oxygen/cabin air ratio increases with an increase in altitude). When the cabin altitude goes above 35 000 ft. the air inlet closes and the wearer breathes 100% oxygen. The user can select 100 % in which case the regulator supplies pure oxygen at all altitudes.
  • If diluter demand or 100% oxygen is selected on the regulator, oxygen will flow as the crewmember inhales and shuts down for exhale.
If the situation calls for it, the user can use the emergency overpressure rotating the knob and receive pure oxygen at positive pressure. Overpressure supply is automatically started, when cabin altitude exceeds 30 000 ft.

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