HVAC Journeyman Practice Exam 2025 - Free HVAC Practice Questions and Study Guide

The ideal location for the terminus of ducts conveying explosive materials is above the roof surface. This positioning is crucial for safety reasons. When ducts are designed to transport potentially explosive substances, placing the vent above the roof allows for the dispersal of any harmful gases or vapors into the atmosphere, reducing the risk of accumulation within the building.

If these materials were to be vented inside the building, there is a heightened risk of creating a hazardous environment, potentially resulting in an explosion or harmful exposure to occupants. Similarly, if the ducts were terminated near the floor, any leaks or releases could lead to dangerous concentrations of explosive materials close to ignition sources. Terminating the ducts at a lateral distance from the wall, while providing some separation, does not adequately mitigate the risk of explosive vapors accumulating in the structure, given that they could still pose a danger to individuals nearby. Thus, positioning the terminus above the roof is the safest alternative and promotes effective ventilation of harmful substances.