What is a key feature of flame effect safety control systems under group VI requirements?

The key feature of flame effect safety control systems under group VI requirements is that the system must be active and control flame effects manually. This requirement emphasizes the importance of direct human supervision and intervention in the operation of flame effects. Manual control ensures that trained personnel can respond immediately to any changes in conditions or emergencies, thereby protecting both the audience and the performers. In settings where flame effects are used, the ability to manually regulate and adjust the flame effects allows for greater flexibility and safety, as operators can make informed decisions based on real-time observations.

The other options do not accurately capture the primary focus of group VI requirements. For instance, the notion that these systems must only work in outdoor environments is incorrect, as flame effects can be effectively utilized in various settings with appropriate safety measures. The inclusion of a secondary independent monitoring system is beneficial but not a defining requirement for all group VI systems. As for integrating audience feedback mechanisms, while important for enhancing the experience, it is not a pivotal feature necessary for the safety control system of flame effects outlined in these specific standards.