stair shaft

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The vertical shaft which contains a staircase.
References in periodicals archive ?
There is no universal consensus on the requirements to prevent smoke from entering the stair shaft.
In an attempt to keep smoke from invading the stairwells, there is a practical upper limit on the amount of air that should be added to the stair shaft.
The values in the figure assume the stairwell doors are tightly fitting (zero gap around the entire door perimeter), and the stair shaft consists of the relatively tight cast concrete construction.
3]/s (636 cfm) per floor is required in order to overcome the fire pressure and keep smoke from entering the stair shaft.
The gap around the door was assumed to be non-existent, and the stair shaft construction was assumed to be very tight.
Comparison of the open area in a typical stair shaft and the open area around the door perimeter shows that construction openings are typically larger than the open area around doors.
A pressure rise of 10-15 Pa was measured across the stair shaft during fire tests in a 10-story fire tower for fire temperatures between 400[degrees]C-800[degrees]C (750[degrees]F -1470[degrees]F) (Tamura 1989).
The COSMO calculations for the capacity of the stairwell pressurization fans and the pressure rise at the fire floor that is necessary to prevent smoke from entering the stair shaft correlate well with field measurements on buildings during non-fire conditions and during simulated fires conducted in fire towers.
The stair shaft is assumed to be made of concrete block with an open area ratio of 8.
Parametric runs with the COSMO program clearly show that a plan to pressurize stairwells can be successful if the stair shaft is well sealed.
One logical way to balance adequate fan capacity with moderate door-opening forces is to overpressurize the stair shaft and then incorporate some type of pressure relief, such as barometric vents, variable-speed fans with feedback, flow bypass, or exit door relief at the ground floor (Tamura 1990, 1992).
The result is a pressurization scheme that creates outward flow of air along the entire height of the stair shaft and a neutral pressure plane that is pushed below the fire floor.