What is the minimum free area required for a permanent outdoor combustion air opening per 3,000 btu/h of total input rating?

The minimum free area required for a permanent outdoor combustion air opening is critical to ensuring that appliances have sufficient airflow for safe and efficient operation. For every 3,000 BTU/h of total input rating for gas appliances, the requirement is established based on guidelines from the National Fuel Gas Code or similar standards.

In this case, the correct requirement is 1 square inch of free area for each 3,000 BTU/h. This means that for every 3,000 BTU/h of energy input, the system must have an appropriately sized air opening to allow adequate combustion air to enter. This is essential to prevent backdrafting, incomplete combustion, or carbon monoxide buildup, all of which can pose serious safety hazards.

To determine the overall combustion air opening needed for larger systems, you can multiply the total BTUs by the established requirement per 3,000 BTU/h. This ensures that appliances function properly while maintaining a safe environment.

Other possible choices provide either insufficient or excessive areas which do not align with the standard requirements, leading to potential issues in appliance performance or safety.