The L rating of a through-penetration firestop system must not exceed which of the following for water measurements?

In firestop systems, the L rating is a crucial measure of the system's ability to limit air leakage, which is particularly important in maintaining the intended fire-resistance rating. The L rating is evaluated through specific water measurements, and it is essential that the values do not exceed the established thresholds to ensure that the firestop will perform effectively in a fire scenario.

The correct answer indicates that the L rating must comply with both specified thresholds. These thresholds are established to ensure optimal performance of the firestop system. Specifically, the first threshold, which is 5.0 cubic feet per minute (cfm) per square foot of penetration, ensures that air leakage through the firestop at a localized level is minimized, providing critical containment during a fire incident. Additionally, the second threshold requires that the total air leakage does not exceed 50 cfm for any area measuring 100 square feet, which ensures that for larger areas, the overall leakage remains controllable and within safe limits.

This dual requirement reinforces the effectiveness of firestop systems in preventing the spread of smoke and flames, maintaining structural integrity during a fire, and thus protecting life and property. Each threshold works in concert to address different scales of air leakage, ensuring comprehensive protection and compliance with building safety codes