What is required for combustion air ducts that pass through walls without dampers?

When combustion air ducts pass through walls without dampers, it is essential for them to be enclosed. Enclosing these ducts helps to maintain the proper airflow and ensures that the air delivered for combustion is not compromised by external conditions. This enclosure also protects the ducts from potential contamination or obstruction, thus preserving the efficiency and safety of the combustion process.

Ensuring that combustion air ducts are enclosed is important for maintaining the necessary temperature and humidity levels required for optimal combustion performance. Additionally, enclosing the ducts can help prevent unwanted air leakage, which can lead to inefficiencies in the system. Overall, this requirement is crucial for ensuring that combustion processes operate safely and effectively.