Combustion air ducts used to supply makeup air must be screened except when terminated in what location?

Combustion air ducts used to supply makeup air must be screened except when terminated in what location?

• A. Exterior wall
• B. Attic
• C. Basement
• D. Crawlspace

Answer: (B)

Makeup air ducts are screened to keep insects, debris, and other contaminants from entering the combustion air path, which helps protect the appliance and maintain clean, unobstructed airflow. There’s an exception for ducts that terminate in an attic. In that case, screening is not required because the attic is considered part of the building’s exterior/ventilated space and introducing a screen there could unduly restrict airflow or lead to buildup of insulation and dust. Allowing the attic termination without a screen ensures reliable makeup air supply while still typically preventing pests in other exterior-air terminations.

Makeup air ducts are screened to keep insects, debris, and other contaminants from entering the combustion air path, which helps protect the appliance and maintain clean, unobstructed airflow.

There’s an exception for ducts that terminate in an attic. In that case, screening is not required because the attic is considered part of the building’s exterior/ventilated space and introducing a screen there could unduly restrict airflow or lead to buildup of insulation and dust. Allowing the attic termination without a screen ensures reliable makeup air supply while still typically preventing pests in other exterior-air terminations.