In order to fully understand the potential impact of smoke management systems for events like those occurring on September 11, 2001, it is important to analyze how various smoke management system configurations might have performed in WTC 1 and WTC 2 had they been available on September 11, 2001 (NIST NCSTAR 1-4D).
The smoke purge approach is based on the documented smoke purge sequence for WTC 1 and WTC 2 as it appears in WTC Instruction Manual No.
The core pressurization approach is a slight variation of the documented smoke purge sequence for WTC 1 and WTC 2, in that the supply fans, rather than the exhaust fans, in the core were activated to pressurize the core, in an effort to prohibit smoke spread into the core from the surrounding office spaces.
The HVAC systems in WTC 1 and WTC 2 were not equipped with operable fire/smoke dampers; thus, it was not possible to configure the system to exhaust and supply to only single floors within a ventilation zone.
Several different design fire scenarios were evaluated for WTC 1 and WTC 2, encompassing the range of expected fires that could be envisioned within the office spaces of the build ing.
* WTC 1 and WTC 2, September 11, 2001 Fire Scenarios (No Shaft Damage)
The fifth fire scenario was an attempt to model smoke management system performance given conditions close to what actually may have existed in WTC 1 and WTC 2 on September 11, 2001.
* The smoke management systems in WTC 1 and WTC 2, which provided the capability for a manual smoke purge (required by the BCNYC for post-fire smoke venting) within an individual HVAC zone on a quadrant-by-quadrant basis, were not initiated on September 11, 2001.