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

The pressure demand type of oxygen system is specifically designed to be used in pressurized aircraft, where the cabin altitude can be significantly higher than the ambient pressure outside the aircraft. In such environments, the oxygen system must be capable of delivering oxygen under pressure to ensure that it is effective at high altitudes.

Pressurized aircraft create a controlled cabin environment, which allows for higher cruising altitudes where oxygen levels are lower. The pressure demand system supplies oxygen when the wearer inhales, and it maintains a higher pressure in relation to the cabin environment. This ensures that the oxygen can flow into the mask effectively and is available for the user at altitude, providing them the necessary breathing support.

Using this type of system in unpressurized aircraft is not ideal because, at lower altitudes, a simple supplemental oxygen system suffices without the need for pressure demand features. Thus, the best application of the pressure demand type oxygen system is exclusively in pressurized aircraft.