Description of Driving Event:
Two technicians were transferring liquid nitrogen from a vendor tanker to a tank trailer. Near the end of the operation, visibility was severely limited due to fog caused by venting nitrogen, leading to a decision to shut down the operation until the visibility improved. While shutting down the transfer operation, the technicians became unconscious due to lack of oxygen but recovered with no ill effects after being rescued by the tanker drivers. Technicians were wearing PPE for protection against frostbite, spills, etc., but did not include equipment to detect lowered oxygen levels or to supply breathing air. At JSC there are a large number of nitrogen containers. The areas surrounding the larger, permanent containers do not normally present pockets in which to trap nitrogen; however, on still days there could be oxygen-deficient areas near the connection the vent, or the 90% fill valve. The smaller portable containers (dewars) could be located in potentially confined areas, also presenting the potential for an oxygen-deficient atmosphere.
Lesson(s) Learned:
Cryogenics are capable of displacing air, resulting in unbreathable, Oxygen-deficient atmospheres.
Recommendation(s):
- Follow your organization's procedures for handling of cryogenics.
- Operations with liquid nitrogen should only be performed using the buddy system and by experienced and qualified personnel familiar with the hazards and safety precautions.
- Resist the urge to rush in and rescue a downed co-worker; 60% of the confined space fatalities happen to the would-be rescuer. If rescue is necessary, use proper protective/breathing equipment.
- Confined Space Entry requirements and procedures must be followed when working with nitrogen in areas that are not well ventilated.
- Improve visibility through the use of portable ventilation fans to disperse the vapor cloud surrounding the operation with necessary.
- Consider use of portable oxygen monitors when working around cryogenic fluids.
Evidence of Recurrence Control Effectiveness:
Safe Alert 1995 SA95013; NASA-JSC Mishap Report 950045
Documents Related to Lesson:
N/A
Mission Directorate(s):
N/A
Additional Key Phrase(s):
- Cryogenic Systems
- Facilities
- Hazardous/Toxic Waste/Materials
- Occupational Health
- Safety & Mission Assurance
Additional Info:
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