46 CFR § 148.325
Wood chips; wood pellets; wood pulp pellets
April 15, 2021
(a) This part applies to wood chips and wood pulp pellets in bulk that may oxidize, leading to depletion of oxygen and an increase in carbon dioxide in the cargo hold.
(b) No person may enter a cargo hold containing wood chips, wood pellets, or wood pulp pellets, unless—
(1) The atmosphere in the cargo hold has been tested and contains enough oxygen to support life; or
(2) The person entering the cargo hold is wearing the appropriate self-contained breathing apparatus.