What is one of the minimum control requirements for group II flame effects?

One of the minimum control requirements for group II flame effects is the provision for an automatic shutoff following a failure. This requirement is critical for ensuring audience safety, as it allows the flame effect system to respond autonomously in the event of a malfunction. Such automatic shutoff mechanisms serve to prevent uncontrolled flame release, which can pose significant risks to both performers and spectators.

In the context of group II flame effects, where the potential for large fire displays exists, having an automatic shutdown mechanism is essential for mitigating hazards. This system can detect anomalies in operation or environmental conditions and activate the shutdown immediately, thereby reducing the likelihood of fire-related incidents and enhancing overall safety.

The other options address different aspects of flame effects but do not fulfill the critical safety requirement that is outlined for group II systems regarding automatic response to failure.