scope:

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.