Where must intumescent firestop materials never be used?

Intumescent firestop materials are designed to expand when exposed to heat, creating a barrier that can effectively prevent the spread of fire and smoke through penetrations in fire-resistance-rated assemblies. However, their use around HVAC fire dampers is problematic. HVAC dampers need to operate reliably under varying temperatures and conditions, ensuring they can open and close as required to maintain air flow and support life safety systems. Using intumescent materials in this context can interfere with the damper’s function, particularly if the material expands in a way that obstructs the proper movement of the damper or alters its performance characteristics.

The other contexts provided in the question do not have the same critical operational requirements that would make the use of intumescent materials problematic. While it is essential to follow manufacturer guidelines and code requirements regarding the use of firestop materials in various contexts, the specific operational needs of HVAC fire dampers make it imperative to avoid intumescent materials in those areas. This preserves the functional integrity and reliability of the fire damper systems, which are crucial for maintaining safe conditions in buildings during a fire event.