What is 'design concentration' in NFPA 2001?

• A. The minimum number of agents in storage
• B. The percent by volume of agent required in the protected space to achieve the intended fire suppression
• C. The time to release
• D. The maximum permissible exposure

Answer: (B)

Design concentration is the percent by volume of the clean agent that must be present in the protected space to achieve the intended fire suppression for the designated fire scenario. It is a dosing target that reflects how much agent, relative to the space’s air volume, is needed to control or extinguish the fire according to NFPA 2001’s criteria. This design value guides system sizing and discharge calculations: the space volume times the design concentration gives the target amount of agent to be released to reach the required protective effect, recognizing that real-world factors like leakage and air exchange will affect the actual concentration. It is not about how much agent is stored, how long it takes to release, or exposure limits.