COMMENT ON PROPOSAL NUMBER: 5000-534
5000- - (8-9.3.2.2):
SUBMITTER: Rick Thornberry
The Code Consortium Inc. / Rep. Alcan Compistes, Inc.
RECOMMENDATION:
Revise 8.9.3.2.2 as indicated below and add a new 8.9.3.2.2.1 as follows: 8.9.3.2.2 Such materials shall be capable of preventing the passage of flame and hot gases sufficient to ignite cotton waste where subjected to NFPA 251 time-temperature fire conditions under a minimum positive pressure differential of 0.01 in. (0.254 mm) of water column (2.5 Pa) for the time period at least equal to the fire resistance rating of the floor exterior curtain wall assembly or 30 minutes, whichever is greater. 8.9.3.2.2.1 Where the fire resistance rating of the floor assembly is less than the time period determined in accordance with 8.9.3.2.2, the time period shall be permitted to be not less than the fire resistance rating of the floor assembly.
SUBSTANTIATION
The explanatory text in the proposal we are proposed to revise by this public comment in Annex A, A.9.3.1 clearly indicates that the problem of the exterior fire exposure resulting from a fire breaking out of a window opening and spreading to the floor above is likely to occur within 15-20 minutes or less of the time from which the fire breaks out of the window (post flashover). At that point it is possible that the fire could spread to the adjacent story through an unprotected exterior window opening above, thus bypassing the joint protection provided at the intersection of the floor assembly with the exterior curtain wall assembly. Since that may be the case, we have proposed that the minimum duration of protection provided by the joint protection method at that intersection should be at least 30 minutes which provides a factor of safety. This time will also help to prevent the spread of the fire via the interior at the intersection of the curtain wall unit the curtain wall has been destroyed by the exposure fire. The breaching of the curtain wall by the fire is also likely to occur within the first 30 minutes of fire exposure, especially where the curtain wall is constructed of glass or light weight metals such as aluminum panels or ACM's. Once that condition occurs, there is no need for the joint protection material to remain in place since the fire can directly attack the floor above by the flame plume escaping from the building on the floor of origin. However, for the case where the exterior wall is provided with a fire resistance rating, we believe it is appropriate to assure that the joint protection material will remain in place and resist the fire penetration for a period at least equal to that of the exterior wall, unless the exterior wall fire resistance rating is greater than that of the floor assembly rating. In that case, the floor assembly rating should govern since that is the basic fire separation element within the interior of the building for preventing fire spread vertically from floor to floor.