Leica EM HPM100

• Accidental release of liquid nitrogen resulting from material damage caused by
some steels and organic materials (plastic, rubber etc.) becoming brittle by
exposure to cold
• Glass Dewar flasks are very sensitive to impact and may burst even if lightly
touched by metal instruments. (Temperature tension because of the high
conductivity of metal)
• O 2 enrichment may occur at the exterior walls of non-insulated tanks and
pipes.
o Creates a fire and explosion hazard if a container is open and during use
where organic substances are present. The vaporizing, very fire-promoting
liquid oxygen may cause spontaneous combustion. Oxygen enrichment can
be recognized by a slight bluish coloring of the liquid nitrogen.
3.5.4.3 Safety precautions and rules for use
• Ensure good ventilation at all times.
• Do not actuate isolation valves on Dewar tanks suddenly, check regularly for
leaks.
• Fill liquid nitrogen only into clean, completely dry containers and apparatus.
• Use only intact Dewar flasks: check the insulation of the flasks regularly by the
vaporization rate. Light boiling at the container walls is an indication of poor
insulation.
• Never seal Dewar flasks with gas-tight covers without a safety valve. Use only
easily operated covers designed for Dewar flasks. Never use closures with a
gasket.
• Thaw ice on apparatus and containers with warm air or hot water only, never use a
flame or red-hot objects.
• If possible, do not use glass Dewar flasks, and particularly do not use glass Dewar
flasks with a capacity greater than 2L. Dewar flasks of metal are preferred.
• Use lightly covered Dewar flasks with a sheet metal mantle for small volumes.
• Large storage containers of stainless steel (over 10L capacity) must be fitted with
a tilt mechanism or a lever system.
• Store containers in a cool, well-ventilated place.
• Provide a fresh-air feed in case of possible enrichment of N2 gas. If applicable,
provide an exhaust system.
• Use only freshly prepared colorless liquid nitrogen.
• Do not spill it when filling and transferring.
• Do not fill container past the fill level with liquid nitrogen. Fill Dewar flasks with a
bottleneck only to clearly below the neck (please note that the length of the Dewar
neck may be different from the length of the lagging).
• Allow overfull flasks to empty partially by leaving them open.
• Do not immerse objects at room temperature in liquid nitrogen.
• Cover small barrels and specimen chambers immediately after use with light
covers that are not gas tight to prevent condensation of oxygen (fire hazard). Move
closed unpressurized containers slowly to prevent spray or overflow.
• Transport only in high-quality insulated containers for very cold gases (cryoflasks).
• Secure containers to prevent falling.
• Avoid any damage and unnecessary agitation.
• Only sealed, unpressurized metal Dewar flasks are permitted in elevators.
Page 9 Leica EM HPM100 Operating Manual Version 12/10