Th e reality highlighted by Budnick and Klote led to the practice of subdividing pressurized stairwells such that pressure gradients caused by stack effect in any single continuous vertical enclosure can be reduced to a more manageable level. In referring to satisfactory pressurization, the authors were referring to the condition wherein nowhere over the stairwell height is the pressure difference greater than the maximum allowable pressure g radient (such that doors can actually be opened) or less than the minimum allowable pressure gradient (such that smoke intrusion from the fire floor is effectively countered).
Budnick and Klote in buildings over 420 feet in height, satisfactory pressurization of a stairwell may be impossible in such tall buildings when all doors are closed. However, as the number of high-rise buildings exceeding 420 feet in height being developed has grown, various challenges associated with this approach have been identified. In the years since these seminal studies, the use of the pressurization approach in stairwells to create “smokeproof enclosures” was widely adopted and usually implemented with relative ease for buildings under 420 feet in height. This work added to general knowledge about flow through openings in buildings, including a key finding that flow coefficients for open doors were about half of what would otherwise be expected. Milke at the Church Street Office Building tests exposed the engineering community to such phenomena as stationary vortex es at open doors. This project built on the findings of earlier studies conducted by entities such as the New York City Fire Department in the early 1970 s and provided further evidence that pressurization of stair shafts could provide smoke-free exits for the fire scenarios and systems tested.
Ontario building code smoke detectors residential series#
The application of pressurization systems to stairwells started to gain momentum following a series of studies including the Atlanta City Building Department full-scale fire tests in the 14-s t o ry Henry Grady Hotel. Historically, pressurization systems were used to protect against the spread of biological and chemical contaminants. Adding to this, there has b een an increasing number of design professionals who have expressed concern over the industry’s reliance on traditional pressurization systems. Within this seemingly limited application, however, there are numerous variations to the approaches taken by the engineers designing the systems and a multitude of disparate code requiremen ts from jurisdiction to jurisdiction. P ositive pressurization approaches intended to keep smoke out of stairw ells have been combined with depressurization or “ pressure sandwich ” approaches intended to control or restrict smoke movement beyond the zone of fire origin. During the past 20 to 30 years, high-rise buildings have almost exclusively made use of one form of active smoke control: the p ressurization method.