Veterinary Andrology and Reproductive Techniques

SAFETY ASPECTS IN HANDLING CRYOGENIC AGENTS

Liquid nitrogen is extremely cold. It should not be touched with bare hand. Up on exposure to skin, it produces frost bite.

• There are number of general precautions and safety practices to be observed because of two important properties of cryogenic fluid – they are extremely cold and very small of liquid is converted into very large amount of gas. When liquid nitrogen evaporates into gasesous form it occupies 700 times its volume.
• Safe handling of liquid nitrogen – Operator guide lines
  • Liquid nitrogen should be handled carefully as it can produce “frost bite” on the skin similar to burn, even if it is in contact for few seconds.
  • The vapour of liqiud nitrogen is also cold and can produce cold burns. Cold vapour can damage delicate tissues such as eyes even if exposed for short period.
  • One should not look into liquid nitrogen container without eye protection
  • Boiling and splashing always occur when filling up a warm container.
  • Always perform these operations slowly to minimize boiling and splashing and keep your eyes away from the container.
  • Always use stainless steel tongs with long handles to remove any object immersed in liquid nitrogen.
  • Loose fitting cryo gloves made of woolen, asbestos or leather can be used for handling.
  • Cold metal may stick to skin and tear the flesh when attempts are made to withdraw the cold object from bare hands or fingers.
  • Specially made cryo gloves are also available for this purpose.
  • Care should be taken to avoid spilling of liquid nitrogen into shoes.
  • Use containers specifically designed to hold liquid nitrogen.
  • All containers have vent or safety device to allow the escape of nitrogen vapour.
  • Inadequate venting or closing tightly can result in excessive gas pressure, which can damage or burst the container.
  • Use only the stopper supplied by the firm. Never plug the container tightly.
  • Ventilation – Always containers in a well ventilated area to prevent excessive concentration of gas.
  • Excessive amounts of nitrogen reduce the concentration of oxygen in the air.
  • When the oxygen level goes below 20.5 per cent can cause asphyxiation.
  • A person can become unconcious without sensing any warning symptoms such as dizziness.
  • Transferring of liquid nitrogen – Use a stainless steel or plastic funnel while pouring liquid nitrogen into another smaller container.
  • The top of the funnel should be partly covered to reduce splashing.
  • When it is not safe to tilt the container, use a discharge tube to remove liquid nitrogen.
  • Specially designed transfer device is also avaiable for safe transfer of liquid nitrogen.
  • Treatment of cold burns – Remove the clothing that may constrict the circulation of the frozen area.
  • Immediately place the affected part in a water bath at 42⁰C and apply water liberally.
  • Never use dry heat which may superimpose a burn upon the frozen tissue.
  • Frozen tissues are painless and appear waxy with yellowish color. They will become painfull, swollen and very prone to infection when thawed.
  • Therefore do not rewarm rapidly if the accident occurs in the field.
  • Morphine and tranqulizers are required to control the pain during thawing and should be done only under professional media supervision.
  • The visible of frost line or water vapour at the top of the container is an indication of damaged container and rapid evaporation of the liquid nitrogen.

TOP