Lab Safety


What are cryogens and why are they hazardous?

Cryogens are liquefied gases that can condense oxygen from the air to create an oxygen rich atmosphere in the nitrogen solution; increasing the potential for fire if flammable or combustible materials are present. Asphyxiation and container over-pressurization are significant hazards due to the large expansion ratio from liquid to gas (700 to 1). Many materials become brittle at extremely low temperatures. Brief contact with materials at extremely low temperatures can cause burns similar to thermal burns. Some of the hazards associated with cryogens are fire, pressure, weakening of materials, and skin or eye burns upon contact with the liquid.

 What is a dewar?

A dewar is an insulated container used to store and transport liquefied gases. It is insulated by a vacuum between its two walls and is equipped with pressure relief device



How should I handle cryogenic materials?

  • All equipment being used should be clean and capable of withstanding very low temperatures
  • Wear safety goggles, proper gloves and closed toe shoes
  • Containers should be heated slowly if need be
  • Use tongs to withdraw objects in cryogenic liquids
  • Always work in well ventilated spaces, especially when filling dewars
  • Do not work with or store large quantities of dry ice in cold rooms
  • Do not overfill the dewar
  • Never leave a filling process unattended

 What do I do if I spill a cryogen?

  • If skin comes in contact with a cryogen or dry ice, run the area of skin under cool or warm water for fifteen minutes (do not use hot or cold water).
  • If your finger gets burned, do not put it in your mouth ( it could burn that as well)
  • Do not try to clean up the spill
  • Notify lab instructor
  • If large amounts of gas are released, leave the area and wait for air exchange


Page last modified December 2, 2010