HAZARDS WITH CRYOGENIC LIQUIDS
Cryogenic liquids are very cold substances [gases which have been condensed into liquids at extremely low temperatures], and are used in research to provide extremely low temperatures for frozen storage and experimentation. The cryogenic hazards are:
·         Cold contact burns and frost Bite
·         Asphyxiation (oxygen deficiency hazard [ODH])
·         Explosion – pressure
·         Explosion – chemical
Cold contact burns and Frost Bite
Liquid or low-temperature gas from any of the specified cryogenic substances will produce effects on the skin similar to a burn. Freezing of skin and body parts due to exposure of low temperatures can leads to permanent damage and discoloration up to loss of limb. Prolonged exposure of cold vapor or gas can damage lungs and the eyes.
Decrease in oxygen content can be caused by a failure/leak of the cryogenic vessel or transfer line and subsequent vaporization of the cryogen. Degrees of asphyxia will occur when the oxygen content of the working environment is less than 20.9% by volume. Effects from oxygen deficiency become noticeable at levels below ~18% and sudden death may occur at ~6% oxygen content by volume.
Explosion - Pressure
Heat flux into the cryogen from the environment will vaporize the liquid and potentially cause pressure buildup in cryogenic containment vessels and transfer lines. Adequate pressure relief must be provided to all parts of a system to permit this routine out gassing and prevent explosion.
In case of the uncontrolled release of cryogens:
·      Leave the area immediately.
·      Never exit the area through a vapor cloud.
·      If you find yourself in the path of a vapor cloud, hold your breath until you are out of the cloud.
If you see a vapor cloud moving toward a stairwell in the tunnel, exit by using the next stairwell away from the cloud.
Explosion - Chemical

Cryogenic fluids with a boiling point below that of liquid oxygen are able to condense oxygen from the atmosphere. Repeated replenishment of the system can thereby cause oxygen to accumulate as an unwanted contaminant. Similar oxygen enrichment may occur where condensed air accumulates on the exterior of cryogenic piping. Violent reactions, e.g. rapid combustion or explosion, may occur if the materials which make contact with the oxygen are combustible.

1 comment: