I used to work as home health nurse. We all carried them - I also kept one in my pocket when I worked in PACU & ICU. They are vital for adding/removing regulators from oxygen tanks. No regulator - no oxygen. That answer took me back! I'm retired now & haven't gone near an oxygen wrench in years! :) Thanks for sharing!!

PS I always love to answer this question when it pops up on FB. I have tarot cards in my purse. One never knows - I might need to check in with The Guides.