two green stripes painted around the top of the
cylinder, while cylinders containing water-pumped
air have one green stripe. Oil-pumped air indicates
that the air or nitrogen is compressed by an
oil-lubricated compressor. Air or nitrogen com-
pressed by a water-lubricated (or nonlubricated)
compressor is referred to as water pumped.
Oil-pumped nitrogen can be very dangerous in
certain situations. For example, nitrogen is
commonly used to purge oxygen systems. Oxygen
will not burn, but it supports and accelerates
combustion and will cause oil to burn easily and
with great intensity.
nitrogen must never be used to purge oxygen
systems. When the small amount of oil remaining
in the nitrogen comes in contact with the oxygen,
an explosion may result. In all situations, use
only the gas specified by the manufacturer or
recommended by the Navy. Nitrogen cylinders are
painted gray. One black stripe identifies cylinders
for oil-pumped nitrogen, and two black stripes
identify cylinders for water-pumped nitrogen. In
addition to these color codes, the exact identi-
fication of the contents is printed in two locations
diametrically opposite one another along the
longitudinal axis of the cylinder. For compressed
air and nitrogen cylinders, the lettering is white.
All compressed gases are hazardous. Com-
pressed air and nitrogen are neither poisonous nor
flammable, but should not be handled carelessly.
Some pneumatic systems operate at pressures
exceeding 3000 psi. Lines and fittings have
exploded, injuring personnel and property.
Literally thousands of careless workers have
blown dust or harmful particles into their eyes by
the careless handling of compressed air outlets.
Nitrogen gas will not support life, and when
it is released in a confined space, it will cause
asphyxia (the loss of consciousness as a result of
too little oxygen and too much carbon dioxide in
the blood). Although compressed air and nitrogen
seem so safe in comparison with other gases, do
not let overconfidence lead to personal injury.
To minimize personal injury and equipment
damage when using compressed gases, observe all
practical operating safety precautions, including
1. Do not use compressed air to clean parts
of your body or clothing, or to perform general
space cleanup in lieu of vacuuming or sweeping.
2. Never attempt to stop or repair a leak while
the leaking portion is still under pressure. Always
isolate, repressurize and danger tag out the
portion of the system to be repaired. For pressures
of 1000 psi or greater, double valve protection is
required to prevent injury if one of the valves
3. Avoid the application of heat to the air
piping system or components, and avoid striking
a sharp or heavy blow on any pressurized part of
the piping system.
4. Avoid rapid operation of manual valves.
The heat of compression caused by a sudden high-
-pressure flow into an empty line or vessel can
cause an explosion if oil is present. Valves should
be slowly cracked open until airflow is noted and
should be kept in this position until pressures on
both sides of the valve have equalized. The rate
of pressure rise should be kept under 200 psi
per second, if possible. Valves may then be opened
5. Do not discharge large quantities of
nitrogen into closed compartments unless
adequate ventilation is provided.
6. Do not subject compressed gas cylinders
to temperatures greater than 130°F.
Remember, any pressurized system can be
hazardous to your health if it is not maintained
and operated carefully and safely.