The building codes require Firestop of all penetrations through fire-rated assemblies. Typically this includes floor/ceilings, elevator shafts, stairwells, corridors, etc. Of course, since the objective of Firestop systems is to contain fire to the area of origin, it is wise to seal all through-penetrations. Firestop also is needed at other joints, voids or gaps in fire-rated assemblies, at air passages and at plenums concealed within floor assemblies.
See USG Fire Stop Systems folder SA727 for tested systems and products.