When can a vent connector be connected to a chimney flue serving a fireplace?

The correct answer indicates that a vent connector can be connected to a chimney flue serving a fireplace only when the fireplace flue opening is permanently sealed. This is important for safety and efficiency reasons. When a fireplace flue is sealed, it can no longer allow combustion gases to escape, prompting the need to prevent any vent connector from interfering with the chimney's purpose. By sealing the flue opening, it ensures that there is no backdraft or the possibility of combustion gases from the vented appliance escaping into the living space, which could pose a health hazard.

This connection is also regulated to ensure that proper venting takes place, and that no harmful gases from multiple sources can mix within the chimney space, which can lead to dangerous situations such as carbon monoxide buildup. Therefore, ensuring that the fireplace flue is permanently sealed is key to safely utilizing the flue for a vent connector, adhering to both safety codes and best practices in installation.