Can a 2 inch diameter round duct be utilized as combustion supply air for an appliance?

The use of a 2-inch diameter round duct as combustion supply air for an appliance is acceptable under specific conditions. The correct answer indicates that a duct of this size can be utilized without additional qualifications or conditions specified within the context of the question.

Typically, combustion air ducts must meet specific size and airflow requirements to ensure that appliances receive adequate air for proper and safe operation. A duct with a 2-inch diameter can provide sufficient airflow to small appliances, particularly those with relatively low input or combustion requirements.

However, there are standards that govern the size of ducts related to the total input of appliances, which could affect the ability to use smaller ducts under certain circumstances. While options involving restrictions or additional conditions might be true in other contexts, they do not apply to the general acceptance of a 2-inch diameter duct for all scenarios involving combustion supply air.

The context of safety and appliance performance underscores the importance of proper duct sizing, but the affirmed answer simplifies the acceptance of this duct size for basic scenarios without complicated conditions.