Which option is not a compliant condition for IMC metallic ducts installed in/under concrete?

Which option is not a compliant condition for IMC metallic ducts installed in/under concrete?

• A. Encased on all sides with minimum of 2 inches concrete
• B. Properly secured before pouring concrete
• C. Sloped to an excessive plenum for drainage
• D. Accessible for cleaning

Answer: (D)

When IMC metallic ducts are installed in or under concrete, the installation must protect the duct and keep it properly in place through the pour. Fully encasing the duct with concrete on all sides (minimum 2 inches) helps shield it from damage and moisture and aligns with this protection goal. Securing the duct before the concrete is poured prevents movement during the pour, which could misalign connections or damage the ductwork. Allowing a sloped path toward drainage (a plenum) helps manage any condensate and keeps moisture from pooling inside the system, which is consistent with maintaining duct performance in a buried installation. Accessibility for cleaning isn’t feasible when the duct is embedded in concrete, so requiring it to be accessible for cleaning would be not compliant. In practice, embedded ductwork is designed to be protected and secured, with any cleaning considerations addressed through accessible sections or cleanouts only where feasible outside the buried sections.

When IMC metallic ducts are installed in or under concrete, the installation must protect the duct and keep it properly in place through the pour. Fully encasing the duct with concrete on all sides (minimum 2 inches) helps shield it from damage and moisture and aligns with this protection goal. Securing the duct before the concrete is poured prevents movement during the pour, which could misalign connections or damage the ductwork. Allowing a sloped path toward drainage (a plenum) helps manage any condensate and keeps moisture from pooling inside the system, which is consistent with maintaining duct performance in a buried installation.

Accessibility for cleaning isn’t feasible when the duct is embedded in concrete, so requiring it to be accessible for cleaning would be not compliant. In practice, embedded ductwork is designed to be protected and secured, with any cleaning considerations addressed through accessible sections or cleanouts only where feasible outside the buried sections.