Which rating classification indicates how a firestop assembly performs when placed in pressurized water for 72 hours?

The W rating classification is specifically designed to indicate how a firestop assembly performs when exposed to water. In particular, it evaluates the assembly's ability to withstand pressurized water for a duration of 72 hours without compromising its integrity or performance. This rating is particularly significant in applications where firestop systems might be subjected to water exposure, such as in areas prone to water intrusion or flooding.

Firestop assemblies with a W rating demonstrate their effectiveness not only in preventing the spread of fire and smoke but also in maintaining their structural capabilities under wet conditions. This characteristic is essential for ensuring safety and compliance in building codes and standards related to fire protection, making the W rating pertinent for applications that might face both fire and water challenges.