What is the requirement for duct systems penetrating nonfire resistance rated floor assemblies regarding fire dampers?

The accurate requirement regarding duct systems penetrating nonfire resistance rated floor assemblies is that fire dampers are not typically needed in residential units. This is primarily because residential construction often follows less stringent fire protection standards compared to commercial or industrial settings. In many codes and regulations, the need for fire dampers is generally focused on areas where there is a higher risk of fire spreading, which is more prevalent in commercial and mixed-use buildings.

In residential units, the duct systems usually do not penetrate through fire-rated barriers, and since the risk of fire spread is managed through different means, fire dampers are excluded from being a requirement. Thus, for residential structures, local code conditions can be satisfied without the necessity of installing fire dampers. This is in contrast to the other choices, as fire dampers are not always necessary, they are mandated for certain occupancies and situations, making the selection stating their non-requirement in residential contexts the correct one.