1-14
The ideal stairtower smoke control system must pressurize the stairway enough to keep the smoke
out, but it must not pressurize it so much that the doors cannot be opened. An example of a
dedicated smoke control system for a stairtower is shown in the figure below.
Figure 1-5. Stairtower Pressurization by Multiple Injections
The figure above shows stairtower pressurization by multiple injections with a supply fan located
at ground level and an exhaust fan located on the building roof.
The table below shows the maximum allowable pressure differential across a door in inches water
gauge (in.) based on how wide the door is and how much force the automatic door closing
mechanism exerts as defined in NFPA 92A. At the pressures shown in the table, the door requires 30
lbf (pounds of force) to open, the maximum limit suggested by the NFPA Life Safety Code (NFPA
101).
Table 1-2. Pressure Differential For Various Door Widths
.
Door Closer
Force (lbf)
Pressure Differential
32 in. 36 in. 40 in. 44 in. 48 in.
6
0.45 0.40 0.37 0.34 0.31
8
0.41 0.37 0.34 0.31 0.28
10
0.37 0.34 0.30 0.28 0.26
12
0.34 0.30 0.27 0.25 0.23
14
0.30 0.27 0.24 0.22 0.21
Continued on next page
Designing a Dedicated Smoke Control System, Continued
Designing the Ideal
Stairtower System
Ensuring Doors
Can Open
Fire Rated
Doors
Exhaust Fan
Air Supply Duct
Air Flow
Air Flow
Supply Fan
Pressure Vents
To Next Page
Loading...
Need help?
General
