General Information
06-237619-001 1-5 April 2020
Note: The term "…sea level equivalent of oxygen…," used above, deserves some clarification.
The allowed exposure limit to air diluted with Kidde IGS agents relates to the residual
oxygen concentration. At sea level the atmospheric pressure is 14.7 psi (101,325 Pa).
The sea level equivalent of oxygen is the "partial pressure" of oxygen in air when the
atmospheric pressure is 14.7 psi. The volume fraction of air that is oxygen is 0.21, or
21%. Thus, at sea level the partial pressure of oxygen in air is 3.09 psi (21,290 Pa).
Thus, the provisions outlined above can be summarized in as shown in Table 1-2.
1-3.2.1 Oxygen Concentration Above or Below Sea Level
At altitudes different than sea level, atmospheric pressure can be calculated using the following
equation:
P(h) = 14.7 (1 - 6.88x10-6 h)5.25588
The partial pressure of oxygen at altitude h is, therefore:
PO2 = 0.21 P(h)
where
h = Altitude above sea level, ft
P(h) = Atmospheric pressure at altitude h, psi
PO2 = Partial pressure of oxygen, psi
The partial pressure of oxygen in an enclosure after the discharge of a gaseous agent system
is given by
PO2,POST-DISCHARGE = 0.21(1-C/100) PO2
where C is concentration, vol %.
Therefore, interpreting the "sea level equivalent" requirement with respect to egress provisions
from a protected space requires that the local altitude be known.
Table 1-2. Egress Time Limits for Spaces Flooded with a Kidde IGS Agent
Agent Conc.
vol %
% O
2
at
Sea Level
P
O2
, psi
Allowed Occupancy
Egress Time
Limit
C < 43 %O
2
> 12 P
O2
> 1.78 Normally occupied 5 min
43 < C < 52 12 > %O
2
> 10 1.78 > P
O2
> 1.47 Normally occupied 3 min
52 < C < 62 10 > %O
2
> 8 1.47 > P
O2
> 1.18 Not normally occupied 30 s
C > 62 %O
2
< 8 P
O2
< 1.18 Unoccupied areas only n/a
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