PE Problem #3

6/6/2019

Inergen (IG-541) is being used for protection of several rooms which contain highly valuable historic documents. If the fire type is considered Class A and the design concentration of Inergen is provided, determine the clean agent-air mixture density.
a. 1.15 kg/cu. m
b. 1.25 kg/cu. m
c. 1.28 kg/cu. m
d. 1.44 kg/cu. m

Solution | Posted 06/07/19

7 Comments

Ralph

6/6/2019 10:18:41 am

NFPA 2001-2015
Table A.5.4.2.2(b): IG-541 & Class A minimum design concentration, Ci = 34.2

C.2.7.1.3, Calculated agent-air mixture density, rho_mi = (rho_e)(Ci/100) + [rho_a * (100-Ci)/100]

rho_e = 1.41 kg/m^3 (Table C.2.7.1.3)
rho_a = 1.202 kg/m^3 (Table C.1)

rho_mi = 1.273 kg/m^3
C?

MDS

6/6/2019 10:30:06 am

Also found in:

SFPE 5th, Table 44.17 Page 1509 for design concentration
SFPE 5th Page 1526 for formula and constants

C. 1.28 kg/m^3

Ryan

6/6/2019 10:41:31 am

I agree with this, but since NFPA 2001 is not on the required material list, you can find this information in the following sections of the SFPE Handbook, 5th ed:

Agent-air mixture density formula is on Page 1526. Identifies air density and vapor densities as well.

The agent concentration for Class A fires is in Table 44.8 on Page 1495 which shows a design concentration of 34.2% for IG-541.

Plugging those values into the equation, I get 1.279, so C.

Amr

6/6/2019 03:57:43 pm

C. 1.28

6/7/2019 05:39:43 am

D 1.43 kg/m3 as per SFPE P 1526

6/7/2019 07:29:34 am

C) 1.28 kg/m3

Brenton

6/7/2019 05:50:32 am

C. 1.28 kg/m3
Design concentration = 34.2%
Density of Inergen = 1.404 kg/m3
Density of air = 1.2 kg/m3
1.404 * .342 + 1.2 * .658 = 1.27 kg/m3

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