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Question asked by Elsa Lopez Diaz on Nov 2, 2017
Latest reply on Apr 17, 2018 by Milton Werner

NFPA 2001 Clarification.

We are under an inert gas system design (IG-541) . Our system is class C fire and according to NFPA-2001 table A. minimun design concentration of 38.5% shall be used.


My concern is related to concetration target to calculate the discharge time. There are two paragraphs on NFPA-2001 that will divert to a different results* For inert gas agents, the discharge time required to achieve 95 percent of the minimum design concentration for flame extinguishment shall  120 seconds for Class A surface fire hazards or Class C hazards,


According to my understanding and values given at A5.4.2.2.B, time should be calculated to achieve 36.5 %(95% of 38.5)* The discharge time period is defined as the time required to discharge from the nozzles 95 percent of the agent mass [at 70°F (21°C)] necessary to achieve the minimum design concentration based on a 20 percent safety factor for flame extinguishment.

According to my understanding, to meet this requirement time should be calculated to achieve 32.5 % (95% of 34.2 Class A fire)


I would need a clarification in order to Know which one is the correct result.