Situations where fire resisting ductwork might be used in lieu of standard ductwork / fire dampers include:
Rooms containing flammable materials or combustible materials with a low ignition point
Lift Shaft ventilation
Passive Air Transfer Ducts
Situations where fire resisting ductwork might be used in lieu of standard ductwork / fire dampers include:
Rooms containing flammable materials or combustible materials with a low ignition point
Lift Shaft ventilation
Passive Air Transfer Ducts