I worked in a semi facility where a respirator line was purged with nitrogen. Through an error, the nitrogen was not removed. 1 guy died. IIRC, no panic, pain or anything. He just passed out and died.
Needless to say, the lock out/tag out procedure got audited.
Lock out/tag out seems like one of those excessive OSHA mandated safety procedures - until the day it saves someone’s life. Where I worked it involved heavy pieces of machinery which somebody had to go inside of to troubleshoot.
One worker guarded the circuit breaker & another monitored the service hatchway until the inside man finished his work and had emerged safely.