Specifications

18
SAFETY BULLETIN
68
Oxygen Enriched Atmospheres
An oxygen enriched atmosphere occurs whenever the
normal oxygen content of the air is allowed to rise
above 23%. While oxygen is nonflammable, ignition of
combustible materials can occur more readily in an
oxygen-rich atmosphere than in air; and combustion
proceeds at a faster rate, although no more total heat
is released.
It is important to locate an oxygen system in a well-
ventilated location since oxygen-rich atmospheres
may collect temporarily in confined areas during the
functioning of a safety relief device or leakage from
the system.
Oxygen system components, including but not limited
to, containers, valves, valve seats, lubricants, fittings,
gaskets and interconnecting equipment including
hoses, shall have adequate compatibility with oxygen
under the conditions of temperature and pressure to
which the components may be exposed in the con-
tainment and use of oxygen. Easily ignitable materials
shall be avoided unless they are parts of equipment
or systems that are approved, listed, or proved suit-
able by test or by past experience.
Compatibility involves both combustibility and ease of
ignition. Materials that burn in air may burn violently
in pure oxygen at normal pressure, and explosively in
pressurized oxygen. In addition, many materials that
do not burn in air may do so in pure oxygen, particu-
larly when under pressure. Metals for containers and
piping must be carefully selected, depending on ser-
vice conditions. The various steels are acceptable for
many applications, but some service conditions may
call for other materials (usually copper or its alloys) be-
cause of their greater resistance to ignition and lower
rate of combustion.
Similarly, materials that can be ignited in air have
lower ignition energies in oxygen. Many such materi-
als may be ignited by friction at a valve seat or stem
packing, or by adiabatic compression produced when
oxygen at high pressure is rapidly introduced into a
system initially at low pressure.
Nitrogen And Argon
Nitrogen and argon (inert gases) are simple asphyxiants.
n
either gas will support or sustain life and can produce
immediate hazardous conditions through the displace-
ment of oxygen. Under high pressure these gases may
produce narcosis, even though an adequate oxygen
supply sufficient for life is present.
Nitrogen and argon vapors in air dilute the concentra-
tion of oxygen necessary to support or sustain life.
Inhalation of high concentrations of these gases can
cause anoxia, resulting in dizziness, nausea, vomiting,
or unconsciousness and possible death. Individuals
should be prohibited from entering areas where the
oxygen content is less than 19% unless equipped with
a self-contained breathing apparatus. Unconscious-
ness and death may occur with virtually no warning if
the oxygen concentration is below approximately 8%.
Contact with cold nitrogen or argon liquid can cause
cryogenic (extreme low temperature) burns and freeze
body tissue.
Persons suffering from lack of oxygen should be
immediately moved to areas with normal atmos-
pheres.
Self-contained breathing apparatus may
be required to prevent asphyxiation of rescue
workers. Assisted respiration and supplemental oxy-
gen should be given if the victim is not breathing. If
cryogenic liquid or cold boil-off gas contacts the skin or
eyes, the affected area should be promptly flooded or
soaked with tepid water (105-115˚F; 41-46˚ C). Do not
use hot water. Cryogenic burns which result in blis-
tering or deeper tissue freezing should be examined
promptly by a physician.
Additional information on nitrogen and argon gas is
available in CGA Pamphlet P-9. Write to:
Compressed Gas Association, Inc
New York, NY 10110