User's Manual

P/N 81-CO2MAN-001 A-1 September 2013
APPENDIX A
FORMULA DERIVATIONS
A-1 THEORETICAL CO
2
EXTINGUISHING CONCENTRATION FOR A TOTAL FLOODING
SYSTEM
If maximum residual oxygen values are known, the theoretical carbon dioxide extinguishing
concentration can be calculated from the following formula.
Equation A.1
Where: = maximum residual oxygen
Diffusion flame fires in most flammable liquids will be extinguished if the oxygen concentration
in the atmosphere is reduced to 15 percent. The theoretical carbon dioxide extinguishing
concentration for most flammable liquids can then be calculated from Equation A.1
A safety factor of 20 percent is then added for fire extinguishing systems. This yields the
following design concentration for most carbon dioxide extinguishing systems.
Therefore, a minimum carbon dioxide concentration of 34 percent by volume is required for all
total-flooding fire extinguishing systems.
The most complete list of theoretical carbon-dioxide extinguishing concentrations and the
suggested minimum design concentration are contained in Table 3-1.
A-2 QUANTITY OF CO
2
REQUIRED FOR A TOTAL FLOODING SYSTEM UNDER A FREE
EFFLUX FLOODING CONDITION
The formula for calculating the quantity of carbon dioxide required to achieve a given
extinguishing concentration under free efflux flooding conditions is.
Equation A.2
Where:
= weight of carbon dioxide, lb.
= enclosure volume, ft.
3
= specific volume of superheated carbon dioxide vapor; 9 ft.
3
/lb.
= design concentration
= natural logarithm
%CO
2
21 O
2
–
21
------------------------
100=
O
2
%CO
2
21 15–
21
-----------------------
100 28.6%==
%CO
2
28.6% 1.2 34.3%==
W
V
S
---
11 C–ln=
W
V
S
C
ln