What must all duct penetrations between floors have?

All duct penetrations between floors must have fireblocking to prevent the spread of fire and smoke between different floors of a building. Fireblocking is a critical fire protection measure that fills any gaps or weaknesses in the building's structure, particularly where ducts pass through floors and ceilings. It serves to compartmentalize areas and slows the movement of fire, enabling better control and improving the safety of both the building and its occupants.

In the context of building codes and fire safety regulations, proper fireblocking ensures that ducts do not act as conduits for fire and smoke, promoting better overall safety in case of a fire emergency. This requirement reflects the broader principle that fire-rated assemblies must maintain their integrity to limit the spread of fire.

Sealing tape and insulation can be useful for other purposes, such as improving HVAC system efficiency and thermal performance, but they do not fulfill the specific requirement for fire safety that fireblocking provides. While registers are essential components of duct systems for airflow management, they are not related to the fire protection strategies necessary for duct penetrations between floors.