In machine control system design, the question of when to use safety-rated equipment is commonly asked; but this is often the wrong question. The defining question should be whether the specific machine control function is a safety function. Determining this is not always straightforward and requires a hazard assessment to identify safety functions (e.g., equipment, devices, or circuits) and the required performance level of the system’s safety-related components. Without a thorough risk assessment, there simply is not sufficient information for a blanket answer on whether it is a safety function or not, and therefore it is not possible to dictate whether or not safety-rated equipment is required.