When designing an NFPA 2001 system, what HVAC/ventilation factors must be accounted for when selecting design concentration and clearance criteria?

• A. Only the room color
• B. Air exchanges, infiltration, and venting
• C. The number of occupants only
• D. The type of lighting

Answer: (B)

HVAC and ventilation control how a clean agent disperses, dilutes, and is removed from a space, so they directly determine both the design concentration and how long the space must be considered cleared. The rate of air exchanges per hour sets how quickly the agent is diluted, which affects the amount of agent needed to achieve the required extinguishing effect and how the hold time will play out in real operation. Infiltration adds unpredictable, uncontrolled air that further dilutes the agent, varying with building tightness and environmental conditions, so it must be accounted for to ensure the design remains effective under real conditions. Venting paths—through doors, ducts, exhausts, and other openings—provide routes for agent removal, influencing how long it takes for concentrations to drop to safe levels after activation. Together, these factors shape the actual performance of the system and the criteria used to specify design concentration and clearance.

Details like room color or lighting don’t affect how the agent behaves or how it clears from the space, so they aren’t part of selecting design concentration or clearance criteria.