The requirements for manual shutdown shall be described [10.3.1 IEC 61511-1:2003].
Operator actions shall be defined. For example, if there is a requirement that the operator is able to manually shut down the process this action shall be defined.
Specify requirements for independence of manual shutdown devices. For example, the manual shutdown concerns only some parts of the plant. Give a detailed description of the involved parts.
Specify the location of manual shut down devices (e.g. control room, field location).
The manual shutdown command from the operator shall not create any other hazards.