Generally safety of operator depends on:
1. Eliminating the Risk by design which the subject of discussion.
2. By procedure i.e. work permit and Risk assessment prior to start the Task ie.propablity and consequences. This depends on the industry and location, i.e. Oil and Gas, indoor or outdoor etc.
3. operator well trained .
In oil and Gas all these solution are required and respected, in addition to that isolation and mechanical interlock is required and has to be well engineered.