WTC 1 and WTC 2 were equipped with a non-dedicated smoke management system (a smoke purge system required by the BCNYC for the purposes of post-fire venting) that utilized the base building HVAC systems that provided normal ventilation to the buildings.
The fire safety plan for WTC 1 and WTC 2 (PANYNJ 1995) defines smoke purge as the removal of smoke and other gaseous combustion products from the (fire) area "after a fire has been extinguished.
Based on the information contained in the fire safety plan for WTC 1 and WTC 2 and WTC Instruction Manual No.
Accounts of a major fire occurring in 1975 on the 11th floor of WTC 1 (Powers 1975; Lathrop 1975) state that the smoke purge sequence pressurized the core with 100 percent outside air and exhausted 100 percent from the office spaces.
Operation of the smoke management system for WTC 1 and WTC 2 could be achieved by controlling the equipment within the individual MERs or at a central control panel located in the Operations Control Center (OCC) located on the B1 level of WTC 2.
In order to respond to the requirements of Local Law 5, the Port Authority initiated a pilot study into the requirements for pressurizing the exit stairs in WTC 1 and WTC 2.
WTC 1 and WTC 2 were equipped throughout with fire dampers at duct penetrations into vertical shafts, consistent with the Building Code of New York City (BCNYC) (New York City 1968).
Emergency power was not retroactively required by the BCNYC, but was provided subsequent to the 1993 bombing for WTC 1 and WTC 2, serving all emergency systems (lighting, fire alarm system, etc.
The following discussion documents the normal operation of the fully functional smoke management systems and their impact on smoke conditions in WTC 1 and WTC 2 on September 11, 2001.
The smoke management systems in WTC 1 and WTC 2 were designed to provide a manually-initiated smoke purge function.