There are 22 type G-1 cylinders arranged in eight systems (see
diagram on page 47B). Sixteen cylinders are banked above the bomb-bay.
The remaining six are buried in the floor of the rear fuselage
compartment. There are also two smaller (type D2) cylinders attached to
the chair of the top-turret gunner. These are not connected to the main
system but must be charged from a portable recharger line. The main
system is charged from a single filler valve located in the left side of
the bomb bay. Each G-1 cylinder, when charged to 450 pounds per square
inch, contains 30 cubic feet of oxygen, and will last one man
approximately 5 hours between 20,000 and 30,000 feet (Auto-Mix "on").