All flame effect control systems must have which of the following capabilities?

The requirement for emergency stop capability in flame effect control systems is crucial for safety. This capability allows for an immediate cessation of all flame effects in the event of an emergency or an unforeseen situation. It is essential to enable operators to quickly respond to changing conditions or hazards, ensuring the safety of the audience and performers. This feature is vital because flame effects, while intended for entertainment, involve inherent risks and potential dangers. In any situation where safety could be compromised, having the ability to instantly stop the operation of these effects is imperative.

In contrast, while remote control operation might be beneficial for convenience and coordination, it's not a mandatory standard across all systems. Input from audience members is not a standard requirement because allowing audience interaction could introduce unpredictable risks. Extended operational time, while possibly advantageous for performance continuity, does not directly enhance the safety measures that need to be prioritized in flame effect scenarios.