In case of loss of the entire oxygen supply of any one system, the
affected crew member may move to any other convenient regulator in the
ship with these exceptions:
(1) The nose gunner may not move to the navigator-bombardier regulator
if the entire system is out.
(2) The radio operator may not move to the bomb-bay regulator if the
entire system is out.
(3) The bottom turret gunner may not move to the camera tunnel
regulator.
This is true because every station, with these three exceptions, has its
own individual oxygen supply. The use of the walk-around bottle is the
same as that described for the B-17. (Page 20).