Lesson Learned/Best Practice Briefing


TitleWorker Sustains Severe Cryo Burns Despite Wearing Appropriate PPE

EventLBNL Event

Event Date06/07/2018

CategoryESH-Cryogens - Cryogen Handling

A recent injury involving a liquid nitrogen fill station has been investigated, and some lessons can be learned from how the event transpired. To summarize:

- Many cryogenic liquid burns occur due to misconceptions about the level of protection offered by cryo gloves. Cryo gloves are NOT cryogenic liquid proof and should never be in direct contact with cryogenic liquids – there is no PPE that will protect from immersion in a cryogenic liquid or contact with a sustained cryogenic liquid stream.

- Cryo gloves are designed to protect users from short duration contact with cryogenically cooled objects and from incidental cryogenic liquid splashes and must never be used to hold cryogenically cooled objects or to intentionally contact cryogenic liquids.

- Cryogenic liquids and cryogenically cooled surfaces can cause burns very rapidly, even through cryo gloves.

- Cryogenic temperatures can produce an anesthetic effect, so that injury from the extreme cold may not cause pain and there may not be any warning that you are being burned.

- Work with cryogenic liquid systems should be engineered to be as hands-off as possible, and tools should be used to manipulate cryogenically cooled objects. If you must place your hands on or near a cryogenically cooled object or where a cryogenic liquid splash is possible, this must be limited to only very short durations, and must be done with cryo gloves that have been inspected and are found to be in good condition.

- EHS does not recommend the use of funnels or other additional loose equipment for filling cryogenic liquid Dewars from fill stations or cryogenic liquid cylinders. If you feel that additional equipment is necessary, please consult with the Cryogenic Liquids SME to ensure that it can be done without significant additional risk.

Actions to Prevent Recurrence
This Lessons Learned is a follow-up to LL18-0013, Worker Sustains Cryogen Burn While Using a Liquid Nitrogen Fill Station.

On June 7th, 2018, a worker was receiving on-the-job training (OJT) for the use of a bulk liquid nitrogen fill station to fill a 4L transfer Dewar flask. The worker had taken all required online safety training and was authorized to work with cryogenic liquids through an active WPC Activity. The worker had never used a liquid nitrogen fill station in the past. On-the-Job training was provided by a more experienced worker, who verbally described the procedure to use the station, then supervised the new worker during the fill operation. While wearing all appropriate and required personal protective equipment (PPE), the worker set up the Dewar and fill hose according to the commonly accepted procedure at that fill station. The worker held the fill wand with one hand and a metal funnel with the other, and later described feeling a cold sensation, but no pain, as the Dewar filled, which took approximately four to five minutes. After carrying the Dewar back to the laboratory, the worker removed the cryogen gloves and discovered a potential injury to both hands. Although it didn't look very concerning at the time, the group called x6999 and summoned an ambulance, which took the worker to the hospital for treatment. With proper medical evaluation, it was determined that the worker had actually sustained severe cryogen burns.

The investigation into this incident revealed two major gaps in training and understanding of cryogenic liquid hazards and risks.

First, many workers were not fully aware of the limitations of the PPE used for handling cryogenic liquids, specifically the cryo gloves. There are multiple possible reasons for this. First, manufacturers and distributors of cryo gloves often use product descriptions that can be misleading to a worker purchasing the gloves. Some examples include," can be worn for extended periods of time"; "provide warmth even after prolonged exposure to cryogenic atmospheres"; and "offer warmth, flexibility, and dexterity even with long exposure to ultra cold".

Rarely do manufacturers or distributors of cryo gloves make clear that the gloves are only intended to protect from cold atmospheres and occasional incidental contact with cold objects. A second reason that many workers may have been unaware of the limitations of cryo gloves is that those who are aware of these limitations often consider that knowledge to be common sense or obvious. More experienced workers may not feel that it is necessary to describe the limitations of cryo gloves during OJT, even to workers who have never worked with cryogenic liquids before. EHS recommends that any work involving cryogenic liquids should be engineered to be as hands-off as possible, and where the worker is absolutely required to touch a cold part of the system or place their hands near a potential cryogenic liquid splash, this must be limited to very brief exposure times and only with proper gloves that are free of any tears or holes.

Second, there is a general assumption that a cryogen-related injury will be accompanied or preceded by pain. In this incident, the worker felt only mild discomfort during the procedure and yet still ended up with severe thermal burns. It is common for people working with extremely cold materials (such as refrigerant gases) to be injured without their knowledge. This is possible because of the interplay between how the nerves perceive temperature and pain, and the anesthetic effect that sets in when the nerves are cooled to about 7 degrees C. The extent of the injury is also not immediately apparent. Anesthesia has occurred, the body has cut off blood flow to the area, and all of the normal biological processes that would cause inflammation don't operate in frozen tissue. Burns from extreme cold tend to look pale and possibly a bit waxy at first, but not blistered or inflamed. This can significantly delay care for someone who has suffered a thermal burn from extreme cold.

Perhaps the clearest lesson that we can learn from this incident is that working safely with cryogenic liquids requires a clear understanding of (a) their hazards and behavior, (b) the equipment used to store and dispense them, and (c) the limitations of the engineering controls and PPE used to handle them safely. To address this:

- EHS is currently working to update the EHS Manual chapter on cryogen safety and the cryogen safety training course to clarify and emphasize the key points of the lessons we learned from this incident.

- A more formal set of OJT guidelines will be developed and made accessible via the Work Planning and Control system.

Effective OJT is the best defense against injuries, but it must prepare the trainee to conduct work safely on their own. This requires the trainee to fully understand not just the proper procedure(s) for the work, but also the hazards of the materials and how best to mitigate their risk. In any work, circumstances may not always be optimal or normal. Therefore it is crucial that OJT prepare the trainee to safely adapt to new situations, including seeking help when needed and speaking up with confidence when something doesn't feel right or safe.

For more information on cryogenic liquids or for questions about this Lessons Learned, please talk to your supervisor, work lead, activity lead, division safety coordinator, or the cryogenic liquids subject matter expert.

Lessons Learned are part of the ISM Core Function 5, Feedback and Improvement. Applicable Lessons Learned are to be considered during working planning activities and incorporated in work processes, prior to performing work.
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