For restrictive openings, what is the requirement for air supply from outdoors?

The requirement for air supply from outdoors for restrictive openings is calculated based on the BTU output of the appliance. The ratio of 1 inch of unobstructed opening for every 4000 BTU is standard for ensuring proper combustion and ventilation when dealing with restrictive spaces. This ratio helps to ensure that there is adequate air supply to support the combustion process in heating equipment, which is critical for both efficient operation and safety.

The adoption of this particular ratio reflects the understanding that proper air supply is necessary to prevent issues such as incomplete combustion, which can lead to dangerous byproducts like carbon monoxide. Additionally, adequate air circulation helps maintain the efficiency of the heating process, thereby optimizing energy use and reducing operational costs. Maintaining this standard is essential within the framework of safety regulations and performance guidelines established by the Maine Journeyman Oil Fuel Board.