The Advanced Photon Source
a U.S. Department of Energy Office of Science User Facility

Experiment Hazard Class 2 – Cryogenic Systems


This hazard classification applies to all experiments involving the use of cryogenic systems and closed cycle refrigerators.

Experiment Category

Experiments involving this hazard class are categorized as medium risk experiments unless other hazard classes apply.

Experiment Hazard Control Verification Statements

General Requirements

The use of detectors/alarms, warning signs, and adequate ventilation are required for areas where release of a cryogen can result in an oxygen deficient atmosphere.  Consult with the divisional ESH coordinator or IH SME for assistance with oxygen deficiency assessments.  Cryogenic systems and vessels are always insulated to reduce heat exchange and are labeled with the common name of the cryogen.  Cryogenic systems are pressure protected and equipment is inspected and maintained.  The APS Engineer in charge of the Liquid Nitrogen Distribution System (LDNS) inspects the LNDS and its associated systems (Programmable Logic Controllers (PLCs) and Automatic Fill Stations) on an annual basis.  Inspection results are uploaded and stored in the APS' Integrated Content Management System (ICMS).  Beamlines are responsible for the inspection of their own branches off of the LNDS.  The use of flammable cryogens requires technical consultation which may be initially obtained from the divisional ESH Coordinator.  A written emergency evacuation response plan must be made available in the work area in which cryogens are in use.  In an emergency DIAL 911 from an Argonne phone or 630-252-1911 from a cell phone.

Storage of Cryogenic Liquids

  • Ensure compatibility of the storage vessel to the cryogen in use
  • Storage vessel is suitably designed and constructed to handle cryogens and in accordance with national consensus standards (49 CFR 178, the ASME Boiler and Pressure Code VIII Division I, DOE order 420.1, Facility Safety, Compressed Gas Association Standards, National Fire Protection Standards, etc.)

Note: Consultation with pressure safety SMEs can be obtained by contacting the Argonne Pressure Technology and Safety Committee chair or members.

Pressure Hazard Controls

  • No part of a cryogenic system can be isolated from a pressure relief device
  • Pressure relief devices cannot be circumvented
  • Pressure relief device has the relief capacity to handle the worst case scenario without causing system over-pressurization
  • The pressure relief device set pressure is at or below the MAWP (maximum allowable working pressure) value
  • Pressure relief devices are to be inspected periodically to confirm operation and verification that the device has not been tampered with or isolated from the system (refer to the content under the General Requirements heading for inspection information/details)
  • Vents (if any) and pressure relief devices discharge to a safe location

Procedural Controls

  • Inform users of the properties and hazards of the cryogen prior to use.  Verify that users are trained in applicable cryogen SOPs, are aware of emergency response plans, and are wearing the proper PPE prior to work with cryogens.
  • Discuss potential consequences of an accidental release with all involved personnel
  • Documented safety review before commissioning of a cryogenic system
  • FAC site services must transport any dewar 25 liters or greater by vehicle from one building to another non-adjacent building when requested
  • Transporting containers and dewars will be done following the guidelines in Laboratory Wide Procedure: LMS-PROC 331, Cryogenic Liquid Safety

Design Reviews and Equipment Inspections

  • Documented safety review of the cryogenic system
  • Ensure dewars or vessels are dry prior to filling the container with a cryogen
  • Verify structural integrity of storage vessels, dewars, and presence/condition of pressure relief devices; vessels owned by ANL are inspected every 3 years
  • Inspect all systems, distribution networks, and devices associated with cryogenic liquids (completed on annual basis by the APS Engineer in charge of the LNDS)

Training – Training must be completed prior to using a cryogenic liquid or system.  Training content should include:

  • Physical, chemical, and physiological hazards associated with cryogenic liquids (SDS)
  • Specific handling hazards in the work environment
  • Descriptions, drawings, and function of the cryogenic container and distribution system
  • Required engineering and administrative controls
  • Review of safe operating procedures
  • Proper use of personal protective equipment
  • A written emergency evacuation response plan made available in the work area
  • First aid measures in the event of an exposure or injury; cold contact burn ("frost bite"): immerse body part in tepid water, do not rub body part, DIAL 911 from an Argonne phone or 630-252-1911 from a cell phone
  • Inspection and maintenance schedules and procedures

Signs and Labeling – Cryogenic systems and equipment are to be labeled with the common name of the cryogen.  Piping is to be labeled with the name of the cryogen and flow direction, per ASME A13.1.  Signs may be obtained from the divisional ESH Coordinator.

Personal Protective Equipment (PPE) – Safety glasses with sideshields (ANSI Z87.1), full face shield, insulating gloves or gauntlets, loose clothing covering arms, pants (without cuffs) long enough to go over the tops of shoes, shoes that cover the entire foot and are made of nonabsorbent material (i.e. leather).  Non-prescription safety glasses and face shields are available in the APS stockroom.

Hazard Information
  • If a cryogenic liquid comes in contact with room temperature, it will boil and create an over-pressurization hazard if excess pressure is not safely relieved.
  • Frostbite may occur because of skin exposure to a cryogen.
  • Physical properties of materials may change when exposed to cryogenic liquids, making some materials more brittle.
  • Oxygen condensation can occur from an atmosphere with liquids that have boiling points below liquid oxygen.  Repeated replenishment of a system may cause oxygen to accumulate as a contaminant.  Fire or explosion could occur if combustibles are present.
  • Due to a high liquid-to-gas expansion rate, evaporation of cryogenic liquid (gas) may cause an oxygen deficient atmosphere based upon the room size and number of air exchanges (the condition may need to assessed or calculated by the divisional ESH Coordinator or IH SME).
  • Grabber-type hand tools should be used when appropriate in lieu of prolonged hand contact with a cryogen or putting a breathing zone into a potentially oxygen deficient atmosphere.
Experiment Authorization
Unless otherwise noted in the approved experiment safety plan, the PSC Deputy Associate Laboratory Director of Operations delegates the authority to authorize an experiment in this hazard class to a member of the APS Experiment Safety Review Board and resident beamline personnel having the authority to authorize experiments as listed in the ESAF system.  Approval by both the host beamline and APS Experiment Safety Review Board are mandatory prerequisites for experiment authorization.

Hazard Control Verification

The PSC Associate Laboratory Director of Operations delegates responsibility for verifying that required controls are in place to the experiment On-Site Spokesperson and Beamline Management.


ANL LMS-PROC-331: Cryogenic Liquid Safety, 2/21/2017 (internal link)

Contact the APS User Safety Program with any questions or if the internal links are not working properly.

Reviewed: July 16, 2020