In the context of fire stop systems, which rating indicates the time for temperature rise measurements?

The T Rating is the correct choice because it specifically relates to the temperature rise measurements associated with firestop systems. This rating indicates how long a firestop assembly can prevent the temperature on the unexposed side from rising above a specified level during a fire exposure scenario.

In firestop testing, the T Rating is critical for ensuring that materials provide adequate thermal protection and can help prevent heat transfer that could lead to structural compromise or ignition of adjacent materials in a fire. Ratings such as F Rating and L Rating focus on different aspects—F Rating is about the fire endurance or integrity of the assembly, whereas L Rating typically deals with the air leakage characteristics of the system. The M Rating, while used in some contexts, does not apply here.

Understanding the T Rating is essential for assessing how effective a firestop system will be in real-world conditions, thus making it a crucial aspect of fire safety design and implementation.