d. Compartments adjacent to damaged area. Major damage is often more extensive than preliminary examination
might indicate. Investigation should cover all spaces, systems, and structures in every compartment adjacent to the
damaged area, even to a depth of two or three compartments in all directions. This is to locate any additional damage
and to establish gas, flooding and fire boundaries around the damaged areas.
e. Inspection of entire ship. If an underwater explosion occurs close to the side of the ship, all voids, tanks, and
lower compartments shall be investigated. All fuel oil tanks on the ship should be investigated for damage by taking
"thief" samples of the oil and testing them for water. Likewise, potable and feed water tanks should be tested for salinity.
There shall be a sounding detail in each repair party, and all crew members should know where and how to sound oil
compartments in their own and adjacent areas.
f. Safety measures.
Investigation of structural damage by visual examination presents many difficulties and dangers.
To do a thorough job, it will often be necessary to open one or more watertight doors or hatches.
It is unwise to open any such closures in the vicinity of damage, and it should be done only after
a thorough investigation by means of soundings, and after obtaining permission from higher
authority whenever the situation permits. Opening a door or hatch to a flooded space will result
in additional flooding.
No watertight door, hatch, scuttle, or manhole should be opened until it is known definitely that the compartment on the
other side is either completely dry or that flooding is minimal enough that opening the closure will not permit flooding to
spread. When a compartment is equipped with a sounding tube, the existence of flooding can be determined by slowly
loosening the sounding tube cap. If air escapes under pressure followed by a trickle of water, a solidly flooded
compartment is indicated, while the escape of air only indicates a partially flooded compartment. Many compartments
are not provided with air escapes; however, this is no bar to investigation. Tapping on a bulkhead with a hammer or
backing off on the air test cap will often disclose the presence of water on the other side; the exact height of water may
be judged by variation in the tones produced when the bulkhead is struck at different levels.
Inaccuracies caused by a hidden frame may be avoided by tapping the bulkhead at two locations.
A dangerous but often necessary method of testing a compartment for flooding is to back off slowly on some of the dogs
which hold a hatch or a door closed. Crew members have made the irretrievable error of first loosening the dogs on the
edge of the door away from the hinges.