User's Manual

Design
September 2013 3-10 P/N 81-CO2MAN-001
3-5.2.4 SPECIAL CONDITIONS
Additional quantities of carbon dioxide are required to compensate for conditions such as
openings in the enclosure, forced ventilation, and abnormally high or low ambient
temperatures. Such conditions could adversely affect the performance of the carbon dioxide
suppression system.
(Equation 3)
Where:
= Minimum quantity of agent to be supplied, lb.(kg)
= Quantity of agent for design concentration from Equation (2) or Equation
(12), lb.(kg)
= Quantity of agent to compensate for uncloseable openings from Equation
(6), lb.(kg)
= Quantity of agent to compensate for forced ventilation from Equation (7),
lb.(kg)
= Quantity of agent to compensate for extreme temperatures from Equation
(10), lb.(kg)
3-5.2.4.1 Uncloseable Openings
Additional carbon dioxide must be provided to compensate for any loss of agent through
openings that cannot be closed prior to or at the start of discharge. The additional quantity
shall be equal to the anticipated loss at the design concentration for the designed duration of
protection, lasting at least 1 minute. This additional quantity of carbon dioxide shall be
combined with the basic concentration quantity.
The leakage rate through an opening in an enclosure depends on many factors. If there is no
forced ventilation, the leakage will depend on the size and location of the openings. It also will
depend on whether there is sufficient leakage in the upper part of the enclosure to allow free
flow of air into the enclosure. Since carbon dioxide is heavier than air, there may be little or
no loss of carbon dioxide from openings in or near the ceiling. Losses in the walls or at the floor
level may be substantial.
To maintain a constant pressure within the enclosure, fresh air must enter through the same
opening as the carbon dioxide exits. Therefore, the effective area of the opening is reduced by
a factor of 2.
(Equation 4)
Where:
= Effective leakage area,
ft.
2
(m
2
)
= Area of all uncloseable opening,
ft.
2
(m
2
)
The leakage rate can be determined using the design concentration, the height from the
centerline of the opening to the ceiling, and the graph in Figure 3-2. If multiple openings exist,
Kidde suggests using the height to the centerline of the lowest opening in the enclosure, as
this will result in the most conservative design.
W
min
W
C
W
L
W
V
W
T
+++=
W
min
W
C
W
L
W
V
W
T
A
L
A
O
2=
A
L
A
O