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Question asked by elsa.lopez on Nov 2, 2017

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.