For an appliance without a draft hood with an input of 50,000 BTUH, what is the minimum combustion air opening required in a tightly constructed building?

When determining the minimum combustion air opening required for an appliance in a tightly constructed building, it's essential to consider the way combustion air is supplied to the appliance. In this scenario, the question specifies that the appliance does not have a draft hood.

In tightly constructed buildings, air cannot easily circulate from outside to provide the necessary combustion air for appliances. Therefore, if an appliance is categorized as having no draft hood, it can sometimes be safely vented to a space that can adequately supply air, even if it seems counterintuitive to suggest that no ventilation might be needed.

This option indicates that the appliance can operate without any additional combustion air openings being necessary because it may be designed to utilize the air present in the room or rely on other means of air supply that do not require venting through an opening.

In practical assessment, it's crucial to ensure that the appliance has access to sufficient combustion air through alternative provisions in tightly sealed environments, making the zero square inches specified in the answer potentially feasible.