How far must a door be kept from swinging within a vented wall furnace air inlet or outlet?

The correct distance a door must be kept from swinging within a vented wall furnace air inlet or outlet is crucial for ensuring proper airflow and safety. Maintaining a distance of 12 inches prevents any obstruction that could interfere with the airflow and combustion process. If a door swings too closely to the vent, it could block air supply needed for the furnace to operate efficiently, potentially leading to inadequate furnace performance or hazards such as carbon monoxide buildup. Proper clearance also allows for better maintenance access and ensures that any exhaust or intake ports remain unobstructed, contributing to the system’s efficiency and safety.

The other choices suggest either too little or too much space, which would not comply with regulations meant to safeguard the operation of heating systems. Therefore, adhering to the established requirement of 12 inches is essential for building codes and best practices in HVAC installations.