Which of the following is NOT a component needed to determine a firestop system?

To understand why water resistance is not a necessary component in determining a firestop system, it's important to recognize the primary purpose of firestop systems. Firestop systems are designed primarily to prevent the spread of fire, smoke, and heat through penetrations in fire-resistance-rated walls and floors. The effectiveness of these systems is generally assessed through specific criteria, which include the characteristics of the penetrating item, the size of the hole or annular space around it, and the F-Rating, which indicates the system's fire-resistance rating.

While water resistance could be a relevant factor in some contexts, it does not play a critical role in the fundamental assessment of a firestop system's ability to perform during a fire. Water resistance might be considered in applications where moisture could affect the integrity of the firestop materials but is not a standard component in the evaluation of fire performance.

In contrast, the other components—such as the penetrating item, hole size or annular space, and the F-Rating—are essential criteria that directly impact how well a firestop system will perform. By understanding these core components, one can evaluate the effectiveness and compliance of firestop systems in protecting buildings from fire hazards.