Final answer:
The number of oxygen masks in a flight deck varies by aircraft type, with commercial airliners typically having at least two for the pilots, and possibly more for additional crew members. Oxygen is stored in high-pressure cylinders that can release oxygen at breathable levels when needed.
Step-by-step explanation:
The number of oxygen masks located in a flight deck can vary depending on the type of aircraft and its configuration. Typically, commercial airliners are equipped with at least two oxygen masks in the flight deck for the pilots. Each pilot has a dedicated mask, ensuring that both can access supplemental oxygen immediately if necessary. This is crucial, as it allows pilots to remain alert and capable of managing the aircraft, even under conditions where cabin pressurization is lost and cabin air becomes insufficient for breathing.
Emergency oxygen masks are designed to deploy automatically in the event of cabin depressurization. On larger aircraft, additional oxygen masks may be available for a third or fourth crew member in the cockpit, or for observer seats if they are present. In general aviation, where smaller aircraft are common, the number of oxygen masks will match the number of seats in the flight deck.
Oxygen in airplanes is often stored as a gas in high-pressure cylinders, though in some military and specialty aircraft, liquid oxygen systems are used. These cylinders are able to hold a significant amount of oxygen because gases are highly compressible. When the oxygen is needed, it's released from the tanks, expanding in volume and decreasing in pressure for use at a breathable level.