46 CFR §35.30-35

1. (a)Where Grades A, B, C, and D liquid cargoes are involved, power driven or manually operated spark producing devices shall not be used in bulk cargo tanks, fuel oil tanks, cargo pumprooms, or enclosed spaces immediately above or adjacent to bulk cargo tanks unless all the following conditions are met:
   1. (1)The compartment itself is gas-free;
   2. (2)The compartments adjacent and the compartments diagonally adjacent are either:
      1. (i)Gas-free;
      2. (ii)Inerted;
      3. (iii)Filled with water;
      4. (iv)Contain Grade E liquid and are closed and secured; or
      5. (v)Are spaces in which flammable vapors and gases normally are not expected to accumulate; and,
   3. (3)All other compartments of the vessel in which flammable vapors and gases may normally be expected to accumulate are closed and secured.
2. (b)This section does not prohibit the use of small hand tools in such locations.