Despatch 926E Equipment Manual (C-155)Rev 2/11 - Manual (Page 13)

8
Installation of Cooling Gas
If the test chamber is to be cooled below chamber ambient temperature, it is necessary
to provide a source of liquefied coolant gas. The type, quality, and handling of the gas
is quite important as is the plumbing used to deliver the gas to the test chamber. Most
test chamber operational problems are caused by improper gas use; thus, the
installation procedures and precautions should be reviewed carefully before operating
the chamber.
The liquid coolant gases should be used only after observing stringent safety
considerations and practices.
Nitrogen is a non-toxic gas, but it can
cause asphyxiation in a confined area that
does not have adequate ventilation. Any
atmosphere which does not contain
enough oxygen for breathing (at least 18%)
can cause dizziness, unconsciousness, or
even death. Carbon dioxide affects the
important acid-base balance within the
body; the body can tolerate increased amounts of carbon dioxide only in limited
concentration. This is recognized in OSHA standards where a Threshold Limit Value of
5,000 parts per million by volume (0.5% concentration) has been adopted. For safety,
concentrations above this level should not be permitted; increased concentrations can
cause bodily harm or death.
Nitrogen and carbon dioxide cannot be detected by the human senses and will be
inhaled like air. If adequate ventilation is not provided, these gases may displace
normal air without warning that a life-depriving atmosphere is developing. Store
containers outdoors or in other well-ventilated areas. Never enter any confined area
where these gases may be present until the area is purged with air and is checked for a
breathable atmosphere.
Never use containers, equipment, or replacement parts other than those specifically
designated for use in nitrogen or carbon dioxide service. Gaseous nitrogen or carbon
dioxide should be released only in an outdoor open area if disposal is required. Liquid
nitrogen or carbon dioxide should be dumped into an outdoor pit filled with clean,
grease-free and oil-free gravel, where they will evaporate rapidly and safely.
WARNING: WARNING: Nitrogen and carbon dioxide
gases can cause asphyxiation and death if
used in confined, poorly-ventilated areas.
Nitrogen and carbon dioxide as liquid or
cold gases can cause freeze burns of the
eyes and skin.