For which type of aircraft oxygen systems is the pressure demand type typically used?

The pressure demand oxygen system is specifically designed for pressurized aircraft, where the oxygen is delivered under pressure, ensuring that it can be effectively utilized at high altitudes where atmospheric pressure is significantly lower. In pressurized environments, such as commercial airliners or military jets, the cabin altitude can be maintained at a much lower level than the true altitude of the aircraft, but if an emergency occurs (such as cabin depressurization), passengers and crew may need supplemental oxygen.

This system works by allowing the user to inhale oxygen only when they take a breath, which helps to conserve oxygen and ensures that the user receives the necessary flow when needed, especially at very high altitudes. It also helps prevent hypoxia, which occurs when there isn't enough oxygen being delivered to the body.

In contrast, other types of oxygen systems are typically used for unpressurized aircraft, where oxygen may be delivered in a non-pressure-demand manner. This distinction highlights the specialized requirements of high-altitude flight environments for pressurized aircraft, making pressure demand systems vital for such operations.