Florida Journeyman Practice Exam

The minimum clearance required to combustibles for duct systems operating between 125°F and 250°F is 12 inches. This requirement is based on safety regulations designed to prevent the risk of fire caused by high temperature ducts. When duct systems operate at elevated temperatures, maintaining an adequate distance from combustible materials is crucial to prevent heat transfer that could ignite these materials.

The specified clearance helps ensure that any heat radiated from the duct does not raise the temperature of nearby combustible surfaces to a point where they could ignite. Allowing for a minimum clearance of 12 inches provides a safe buffer zone, which is important for both residential and commercial installations.

While the other options suggest smaller clearances, they do not meet the safety standards set forth for duct systems in that temperature range. Compliance with these standards is essential for effective fire prevention and ensuring the safety of occupants in any structure where such duct systems are installed.