What is the minimum opening size required for the passage of an air supply?

The correct answer, which indicates a minimum opening size of 1 square inch per 1000 BTUH, reflects standard requirements for air supply openings in HVAC systems. The reasoning behind this requirement is to ensure that there is adequate air flow into a system to maintain proper combustion and ventilation, particularly in confined spaces like utility rooms or basements where heating devices might be located.

This standard ratio helps to prevent issues such as backdrafting, which can occur when the air supply is insufficient for the equipment's BTU output, leading to inefficient performance or unsafe conditions with potential gas appliances. Additionally, it promotes energy efficiency by ensuring that the heating system operates within its optimal parameters, effectively circulating warm air throughout the space being heated.

In contrast, the other answer choices provide ratios that do not align with industry standards for air flow requirements. Proper ventilation is critical in construction and HVAC practices, and adherence to the correct minimum opening size is essential for safety and effectiveness in heating systems.