Thermo Scientific 700 Series Manual page 90

Appendix A
Handling Liquid Nitrogen
Use proper transfer equipment.
Use a phase separator or special filling funnel to prevent splashing and
spilling when transferring liquid nitrogen into or from a dewar or
refrigerator. The top of the funnel should be partly covered to reduce
splashing. Use only small, easily-handled dewars for pouring liquid. For
the larger, heavier containers, use a cryogenic liquid withdrawal device to
transfer liquid from one container to another. Be sure to follow
instructions supplied with the withdrawal device. When liquid cylinders
or other large storage containers are used for filling, follow the instructions
supplied with those units and their accessories.
Do not overfill containers.
Filling above the bottom of the necktube (or specified maximum level) can
result in overflow and spillage of liquid when the necktube core or cover is
placed in the opening.
Never use hollow rods or tubes as dipsticks.
When a warm tube is inserted into liquid nitrogen, liquid will spout from
the top of the tube due to gasification and rapid expansion of liquid inside
the tube.
Warning Nitrogen Gas Can Cause Suffocation Without Warning! ▲
Store and use liquid nitrogen only in a well-ventilated place.
As the liquid evaporates, the resulting gas tends to displace the normal air
from the area. In closed areas, excessive amounts of nitrogen gas reduce
the concentration of oxygen and can result in asphyxiation. Because
nitrogen gas is colorless, odorless and tasteless, it cannot be detected by the
human senses and will be breathed as if it were air. Breathing an
atmosphere that contains less than 18% oxygen can cause dizziness and
quickly result in unconsciousness and death.
Note The cloudy vapor that appears when liquid nitrogen is exposed to the
air is condensed moisture; not the gas itself. The issuing gas is invisible. ▲
Never dispose of liquid nitrogen in confined areas or places where others
may enter.
Disposal of liquid nitrogen should be done outdoors in a safe place. Pour
the liquid slowly on gravel or bare earth where it can evaporate without
causing damage. Do not pour the liquid on pavement.
Thermo Fisher Scientific 7010708 A -3