Are you asking what the design concentration is for a Class C fire? What does the room contain? If its electronics, you also have a Class A fire hazard.
The design concentration is established in its listing. Therefore you need to contact the manufacturer and determine what is required for a Class A fire hazard. See NFPA 2001, section 3-4.2.2. Additionally, NFPA 2001 requires that you provide a safety factor of 1.2.
as posted before yes if the circuit is live you have a class C fire But what is normaly burning is the class A material and you design to that and most of the clean agents carry class C rating also and as stated before each manufacter will have its own requirements for concentration.