What is the minimum vertical clearance from the ground to the lowest portion of a combustion air duct?

The minimum vertical clearance from the ground to the lowest portion of a combustion air duct is set at 12 inches to ensure that the duct is above potential water accumulation, debris, and contaminants that could obstruct airflow or affect combustion efficiency. This clearance is crucial for maintaining the integrity of the air intake system, preventing blockages that could lead to inadequate air supply for combustion.

A clearance of 12 inches is often aligned with building and safety codes, which emphasize the need for proper installation practices to promote safety and efficiency in heating systems. Maintaining this height also helps avoid potential issues from landscaping, snow, or other environmental factors that could impede the duct's performance.