Firestop pillows are most suitable for which applications?

Firestop pillows are specifically designed to be used in openings that require removable fire protection. This is particularly useful in applications where penetration seals need to be temporary, allowing for future access or adjustments. Firestop pillows can easily be inserted and removed as necessary, providing a flexible solution that maintains fire resistance while accommodating changes in building use or structure.

In contrast, the other options pertain to scenarios where other forms of firestop systems, like solid firestop materials or caulks, would be more appropriate. For example, electrical conduits in walls typically involve more rigid firestop materials to securely seal around the conduit and maintain fire integrity. Flexible joints require systems designed to accommodate movement, which does not align with the primary use of firestop pillows. Fastening ductwork tends to involve securing ducts in place with non-removable firestop solutions to ensure long-term fire protection. Therefore, the specific capability of firestop pillows to provide removable fire protection makes them most suitable for openings that require temporary solutions.