Determining The Amount Of Pressure Needed; Minimum Pressure Differential To Pressurize Fire Zone - Andover Controls Infinity Manual

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Determining the Amount of
Pressure Needed
Since air pressure is what keeps smoke from spreading, the primary
design factors are the amount of pressure that you need to confine the
smoke and the size of the system used to create this pressure.
For the smoke control system to create a barrier of air pressure between
the smoke zone and surrounding zones, the amount of pressure required
varies with the height of the ceiling and whether or not the building has
a sprinkler system. The next table shows the minimum pressure
differential needed to keep smoke out of surrounding rooms.
Table 1-1. Minimum Pressure Differential to
Pressurize Fire Zone
Sprinkler Ceiling
System Height
Yes Any
No 9 ft
No 15 ft
No 21 ft
For buildings without sprinklers and with ceiling heights not shown in
the table, you can use the following formula to determine the minimum
amount of pressure needed to keep smoke out:
MinimumPressure =
H is the distance between the fire space and a surrounding space where
the pressure differential is zero. A figure of the floor to ceiling height
is a conservative estimate.
T is the absolute room temperature of the surrounding zones measured
o
in °R (degrees Rankine). Typically, T
from °R to °F is: °R = °F + 460.
T is the absolute temperature of the hot gases in the fire zone. It is also
f
measured in °R. Typically, T
1-10
The Fundementals of Smoke Control
Minimum Pressure
Differential (wg)
0.05
0.10
0.14
0.18
1 1
× ×
7.64 H ---- - – --- - +
T T
o f
2
- -
3
= 530° R (70° F). The conversion
o
is 2160° R (1700° F).
f
Infinity Smoke Control Guide
SafetyFactor
TOC