Hazards of Cryogens

Cryogenic liquids (or cryogens) are liquified gases that are cooled below room temperature-most cryogenic liquids are below -150°C. When a small amount of cryogenic liquid is converted into gas, a very large volume of gas is created. Under WHMIS, cryogenic liquids are classified as compressed gases.


Extreme Cold

Cryogens can freeze flesh, causing painful blisters, much like a burn. Prolonged exposure can cause frostbite with pain occuring only when the flesh thaws. Flesh can stick to cold metals.



Cryogens expand into large volumes of gas that can displace air. For example, 1L of liquid nitrogen forms nearly 700L of nitrogen gas at room temperature. The gas formed is often cold and pools on the floor or lower areas. In enclosed areas, death or coma from oxygen deficiency may occur. Do not enter an oxygen deficient atmosphere even to rescue someone. Always store dewars in well-ventilated areas. Never enter the cryogen facility if the oxygen warning sensor alarm is sounding. The oxygen level alarm and sensor are located on the wall next to the freight elevator in the Cryogenic Facility.


Toxic Hazards

Toxic cryogens will release toxic gases. Read the MSDS that came with the liquid.


Obscured Vision

The vapour formed from cryogens fall down forming a ground level fog that obscures the floor. Beware of trip hazards.


High Pressure

Sealed systems containing cryogens may form extremely high pressures, enough to rupture or explode. Always have a relief vent on a cryogen dewar.


Dewars in High Magnetic Fields

Superconducting magnets are rountinely filled with cryogens. The dewars used for this purpose must be non-magnetic.


Liquid Oxygen

Liquid oxygen can make materials burn that are considered non-combustable like teflon or aluminum. Organic materials may react explosively. Liquid oxygen often forms on the outside of transfer lines.



  • Do wear goggles, cryogen gloves and loose fitting clothing with no pockets when handling cryogenic liquids.
  • Do read the MSDS that came with the liquid. 
  • Do transport cryogenic liquids in containers approved for such use. 
  • Do avoid activities that will cause splashing of the liquid.
  • Do use cryogens in well-ventilated areas. 
  • Do cover dewars to revent liquid oxygen build-up.


  • Do not enclose cryogenic liquids without a vent. 
  • Do not use large quantities of cryogenic liquids without proper ventilation. 
  • Do not enter the cryogenic facility if the alarm is sounding.
  • Do not tip or spill dewars.


Alarm levels in the Cryogenic Facility

Oxygen level Alarm
19.50% Intermittent alarm
Continous alarm and solenoid valves shut off the N2 system.
Leave the area at once and report this to the ChemStore manager in LM20.
19.10% The oxygen level alarm and sensor are located on the wall next to the freight elevator in the Cryogenic Facility.