IMCA

A welder entered a 86cm (34”) pipe through a 50cm (20”) opening to check on welding being carried out. He was found unconscious by another worker who had noticed his absence, and called the emergency team. First aid was provided by the shipyard rescue teams and he was then taken to a local hospital, where, though care was continued, he was pronounced dead.

https://www.imca-int.com/resources/safety/safety-flashes/0225-confined-space-entry-hot-work-fatality/