Which rating is most significant for assessing the temperature control of a firestop system?

The D rating is most significant for assessing the temperature control of a firestop system because it specifically measures the system's ability to manage heat transfer. This rating indicates the level of temperature rise that may occur on the non-fire side of the firestop during a fire exposure. In the context of firestop systems, temperature control is critical as it helps to prevent the spread of heat and flames, protecting the integrity of adjacent spaces and building occupants.

While other ratings like the F, FS, and L ratings evaluate different performance aspects such as fire resistance duration and leakage rates, they do not directly assess the temperature control properties as the D rating does. Understanding the significance of the D rating assists inspectors in selecting appropriate firestop systems based on their thermal performance in addition to their protective features against the spread of fire.