My nephew is a scuba diver and works for a company that does offshore drilling. Through him is the first time I had ever heard of heliox. He had a friend that was his diving partner that almost lost his life two years ago on a dive. They were diving at very deep depths and his partner just couldn’t get enough air. If I remember correctly, they were diving at around 400 feet. He said his partner was struggling because he wasn’t moving air smoothly enough.
When they signaled to bring him up, he had uncontrollable shaking. He was flown out to the nearest hospital and was there for about a month. He’s not diving again but he is okay. It was after that incident that I learned about what heliox was and what its purpose was.