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Lab Safety Manual
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1st Rule of Lab Safety
Haz-Waste No-No
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Updated December
1999
General Safety
Section 2.4 - Compressed Gas Safety
D. Cryogenic Liquids
A number of hazards may be present from the
use of cryogenic liquids in the laboratory. Employees should be properly trained in these
hazards prior to use. The transfer of liquefied gases from one container to another should
not be attempted for the first time without the direct supervision and instruction of
someone experienced in the operation.
Fire/Explosions
- Neither liquid nitrogen nor liquid air should be used to
cool a flammable mixture in the presence of air because oxygen can condense from the air
and lead to a potentially explosive condition.
- Adequate ventilation must always be used to prevent the
build-up of vapors of flammable gases such as hydrogen, methane, and acetylene.
- Adequate ventilation is also required when using gases such
as nitrogen, helium, or hydrogen. In these cases, oxygen can be condensed out of the
atmosphere creating a potential for explosive conditions.
Pressure
Cylinders and other pressure vessels used for the storage and handling of liquefied gases
should not be filled to more than 80% of capacity, to prevent the possibility of thermal
expansion and the resulting bursting of the vessel by hydrostatic pressure.
Embrittlement of Structural Materials
Appropriate impact-resistant containers must be used that have been designed to withstand
the extremely low temperatures.
Contact With and Destruction of Living
Tissue
Even very brief contact with a cryogenic liquid is capable of causing tissue damage
similar to that of thermal burns. Prolonged contact may result in blood clots that have
potentially serious consequences. In addition, surfaces cooled by cryogenic liquids can
cause severe damage to the skin. Gloves and eye protection (preferably a face shield)
should be worn at all times when handling cryogenic liquids. Gloves should be chosen that
are impervious to the fluid being handled and loose enough to be tossed off easily.
Appropriate dry gloves should be used when handling dry ice. "Chunks" or cubes
should be added slowly to any liquid portion of the cooling bath to avoid foaming over.
Asphyxiation
As the liquid form of gases warm and become airborne, oxygen may be displaced to the point
that employees may experience oxygen deficiency or asphyxiation. Any area where such
materials are used should be well ventilated. For this same reason, employees should avoid
lowering their heads into a dry ice chest. (Carbon dioxide is heavier than air, and
suffocation can result.)
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Disposal of Broken Glassware
