46 CFR § 154.1345 - Gas detection.
(a) Each vessel carrying a cargo that is designated with an “I” or “I and T” in Table 4 must have:
(1) A fixed flammable gas detection system that meets § 154.1350; and
(2) Two portable gas detectors that can each measure 0 to 100% of the lower flammable limit of the cargo carried.
(b) Each vessel carrying a cargo that is designated with a “T” or “I and T” in Table 4 must have:
(1) Two portable gas detectors that show if the concentration of cargo is above or below the threshold limit value listed in 29 CFR 1910.1000 for that cargo; and
(2) Fixed gas sampling tubes in each hold space and interbarrier space with:
(i) The number of tubes specially approved by the Commandant (CG–OES);
(ii) Each tube valved and capped above the main deck unless it is connected to a fixed toxic gas detector;
(iii) If the vessel carries cargo that is heavier than the atmosphere of the space, each tube's open end in the lower part of the space;
(iv) If the vessel carries cargo that is lighter than the atmosphere of the space, each tube's open end in the upper part of the space;
(v) If the vessel carries cargo that is heavier than the atmosphere of the space and another cargo that is lighter than the atmosphere of the space, tubes with their open ends in the lower part of the space and tubes with their open ends in the upper part of the space; and
(vi) If the vessel carries cargo that can be both heavier and lighter than the atmosphere of the space, tubes with their open ends in the lower part of the space and tubes with their open ends in the upper part of the space.
(c) A vessel that carries methyl bromide or sulfur dioxide must have a fixed gas detection system that is not located in a gas-safe space.
(d) A vessel that carries sulfur dioxide must have a fixed gas detection system that meets § 154.1350 except paragraph (j).
(e) Each alarm under § 154.1350(e) on a vessel that carries methyl bromide or sulfur dioxide must be set at or below the threshold limit value listed in 29 CFR 1910.1000 for the cargo carried.