A vent connector shall NOT connect to a chimney flue serving a fireplace unless what condition is met?

A vent connector should not connect to a chimney flue serving a fireplace unless the fireplace flue opening is permanently sealed. This condition is crucial because it ensures that any gases or byproducts from the venting of the appliance are not allowed to enter the fireplace system. An improperly connected vent could lead to backdrafting, where gases intended to vent outside could instead flow back into the living space, posing serious health risks due to carbon monoxide and other hazardous emissions.

Permanently sealing the fireplace flue opening effectively isolates the fireplace from the vent system, ensuring safety and compliance with code regulations. This practice prevents any chance of flue gases mixing with those from the fireplace, maintaining clear venting paths for all appliances served by the chimney.

Other considerations related to the other options might include that simply blocking a flue opening does not guarantee safety, as gases could still accumulate or create pressure issues within the system. Disassembling the chimney or declaring the fireplace as no longer in use are measures that do not provide the same level of assurance in preventing unsafe conditions related to venting. Thus, permanently sealing the fireplace flue opening is the best practice to ensure the safe operation of venting systems connected to a chimney.