What is a safety feature required for vented decorative appliances?

A safety feature required for vented decorative appliances is the automatic shutoff valve. This device is crucial as it ensures that the appliance can automatically stop the gas flow in case of a malfunction or if the flame goes out unexpectedly. This feature helps to prevent the accumulation of combustible gases, potentially reducing the risk of fires or explosions, thus promoting a safer environment when using decorative vented appliances.

While other options like manual ignition systems or safety glass doors may enhance safety in various contexts or specific appliance designs, they do not serve the same critical function of managing gas flow and preventing hazardous situations in the case of an operational failure. Flame-proof casing, while important in certain applications, does not address the specific risks associated with gas appliances in the same direct manner as an automatic shutoff valve. Therefore, the importance of the automatic shutoff valve is paramount in ensuring the safe operation of vented decorative appliances.