Located under the burner of a FVIR tank, which metal plate allows combustion air into the combustion chamber but keeps flames from escaping downward?

The flame arrestor plate plays a crucial role in the safe operation of FVIR (Flame Vapor Ignition Resistant) water heaters. It is specifically designed to allow the necessary combustion air to enter the combustion chamber while effectively preventing flames from escaping downward. This design is essential for minimizing the risk of a fire hazard, particularly in environments where flammable vapors may accumulate.

The flame arrestor plate utilizes a mesh or perforated configuration that permits air flow while acting as a barrier to flames. This feature helps protect the surrounding area from potential ignition sources, ensuring that the water heater operates safely even under conditions that might otherwise allow flames to escape.

In contrast, the other terms do not accurately describe this safety feature. A flame protector generally refers to any device that guards against flames but is not specific to the function of managing air intake and flame containment. An ignition shield, while useful in protecting sensitive components from heat, does not specifically address the airflow and flame containment necessary in this context. Ventilation plates primarily serve to enhance air circulation without the specific flame arresting capability. Thus, the flame arrestor plate is the correct answer as it effectively combines air intake with flame containment in FVIR systems.