6-20 Change A
U.S. Navy Diving Manual—Volume 2
also inadvertently take polluting materials into the mouth, posing both physiolog-
ical and psychological problems. External ear prophylaxis should be provided to
diving personnel to prevent ear infections.
6-6.7
Altitude Diving. Divers may be required to dive in bodies of water at higher alti-
tudes. Planning shall address the effects of the atmospheric pressures that may be
much lower than those at sea level. U.S. Navy Air Decompression Tables are
authorized for use at altitudes up to 300 feet above sea level without corrections
(see paragraph 9-12). Transporting divers out of the diving area, which may
include movement into even higher elevations either overland or by plane,
requires special consideration and planning. The Diving Supervisor shall be alert
for symptoms of hypoxia and decompression sickness after the dive due to the
lower oxygen partial pressure and atmospheric pressure.
6-6.8
Underwater Obstacles. Various underwater obstacles, such as wrecks or
discarded munitions, offer serious hazards to diving. Wrecks and dumping
grounds are often noted on charts, but the actual presence of obstacles might not
be discovered until an operation begins. This is a good reason for scheduling a
preliminary inspection dive before a final work schedule and detailed dive plan is
prepared.
6-6.9
Electrical Shock Hazards. Electrical shock may occur when using electric
welding or power equipment. All electrical equipment shall be in good repair and
be inspected before diving. Although equipped with test buttons, electrical
Grounds Fault Interrupters (GFI) often do not provide any indication when the
unit has experienced an internal component failure in the fault circuitry. There-
fore, GFI component failure during operation (subsequent to testing the unit) may
go unnoticed. Although this failure alone will not put the diver at risk, the GFI will
not protect the diver if he is placed in contact with a sufficiently high fault current.
The following is some general information concerning GFIs:
GFIs are required when line voltage is above 7.5 VAC or 30 VDC.
GFIs shall be capable of tripping within 20 milliseconds (ms) after detecting a
maximum leakage current of 30 milliamps (ma).
GFIs require an established reference ground in order to function properly.
Cascading GFIs could result in loss of reference ground; therefore, GFIs or
equipment containing built-in GFIs should not be plugged into an existing GFI
circuit.
In general, three independent actions must occur simultaneously to electrically
shock a diver:
The GFI must fail.
The electrical equipment which the diver is operating must experience a
ground fault.
