Chapter 8, Chemical Hygiene Plan: Cryogenic Liquids and Compressed Gases

Revised January 2022

Cryogenic liquids are materials with a boiling point of less than – 100 °F (-73 °C); common examples include liquid nitrogen, helium, and argon, and dry ice/alcohol slurries. Cryogenic liquids undergo large volume expansion upon transition to the gas phase, for example, one volume of liquid nitrogen vaporizes to 694 volumes of nitrogen gas. Consequently, the warming of a cryogenic liquid in a sealed container produces high pressure, which can rupture the container.

Hazards of cryogenic liquids include fire (in the case of flammable or oxidizing materials), pressure buildup, explosion, as well as severe frostbite (on contact with skin) and asphyxiation (due to depletion of available oxygen). Additionally, cryogenic liquids such as liquid nitrogen have boiling points below that of oxygen and are capable of condensing atmospheric oxygen, resulting in a localized, oxygen-enriched environment through formation of liquid oxygen. Liquid oxygen in combination with many organic (oxidizable) materials can result in a violent reaction. Systems that incorporate liquid nitrogen traps must never be opened to the atmosphere until the trap is removed from the coolant.

Note: Plastic mesh will not stop small glass fragments

Compressed gases are considered more hazardous to handle than liquids or solids because of the high pressure involved and the ability of the gas to spread rapidly when released. Additionally, many compressed gases are flammable, toxic or corrosive.

As a State facility, the University is covered by the International Fire Code (IFC). The IFC specifies maximum allowable quantities of hazardous compressed gases per designated fire control area. Fire control areas generally consist of multiple laboratory rooms, making it difficult to assign a maximum allowable quantity for each room. NFPA 45, Standard on Fire Protection for Laboratories Using Chemicals, also applies in a regulatory sense to the University. This standard provides guidance on the maximum number of compressed gas or liquefied gas cylinders per laboratory (500 ft2 or less) as shown below. Contact the University CHO for more specific guidance.

Additional information on the safe handling and use of compressed gases is available from the Compressed Gas Association, Matheson Tri-Gas, and in the Air Liquide Design and Safety Handbook.

Chapter 9: Particularly Hazardous Substances