Steel doors used in fire-rated assemblies must carry a listing from a nationally recognized testing laboratory (NRTL) such as UL or Intertek, certifying compliance with NFPA 80 and the applicable fire-resistance rating (e.g., 20-minute, 45-minute, 90-minute). Foreign manufacturers must obtain this listing through testing at an accredited facility; the listing label must be affixed to the door before installation and is typically verified by the authority having jurisdiction (AHJ) during inspection.

A door slab alone and a pre-hung unit (slab plus frame, hinges, and hardware) may be classified differently depending on whether the complete assembly is presented as a set. Pre-hung units with all components imported together are often classified as a complete door assembly, while separately imported slabs and frames may each be classified under their own provision. Consulting a customs broker before structuring the shipment can prevent post-entry reclassification.