HVAC Journeyman Practice Exam 2026 - Free HVAC Practice Questions and Study Guide

The minimum requirement for metal ducts installed in or under a concrete slab is that they must be encased in at least 2 inches of sand. This is to ensure that the metal ducts are protected from potential damage caused by the surrounding concrete and any shifting or settling that might occur over time. Sand provides a cushioning effect, preventing direct contact between the metal ducts and the concrete, which could lead to corrosion or physical damage to the ducts. Encasing ducts in sand also helps to maintain the integrity of the duct system, ensuring efficient operation without the risk of leaks or blockages due to constriction or impact from the concrete.

While insulation and other protective measures are important for HVAC systems, in the context of installation under a concrete slab, proper protective encasement in sand meets the specific need for safeguarding ductwork in potentially vulnerable environments. This practice aligns with industry codes and standards to ensure the longevity and efficiency of the HVAC system.