154.1828—Spaces containing cargo vapor: Entry.
(a)
No person may enter a cargo handling space without the permission of the master or without following a safety procedure established by the master.
(1)
The space is free of toxic vapors and has an oxygen concentration of at least 19.5 percent oxygen by volume; or
(2)
Those entering the space wear protective equipment with breathing apparatus and an officer closely supervises the entire operation in the space.