The minimum F rating for firestopping on a two-hour firewall is 120.

The minimum F rating for firestopping on a two-hour firewall is 120.

• A. 60
• B. 120
• C. 240
• D. 360

Answer: (B)

The key idea is that firestopping must meet or exceed the fire-resistance rating of the assembly it passes through. The F rating marks how long a firestop system remains effective under standard fire testing, expressed in minutes. For a two-hour firewall, you need a firestop system that lasts at least 120 minutes. That makes 120 the minimum acceptable F rating. A 60-minute rating would not meet the requirement, while 240 or 360 would exceed it—but since the question asks for the minimum that satisfies the two-hour wall, 120 is the correct choice.

The key idea is that firestopping must meet or exceed the fire-resistance rating of the assembly it passes through. The F rating marks how long a firestop system remains effective under standard fire testing, expressed in minutes. For a two-hour firewall, you need a firestop system that lasts at least 120 minutes. That makes 120 the minimum acceptable F rating. A 60-minute rating would not meet the requirement, while 240 or 360 would exceed it—but since the question asks for the minimum that satisfies the two-hour wall, 120 is the correct choice.