In a protected enclosure, how should the area of unclosable openings be treated?

• A. Kept to a minimum
• B. Kept to a maximum
• C. Not specified
• D. Completely sealed

Answer: (A)

In a protected enclosure, the goal is to maintain the required clean-agent concentration long enough to suppress the fire while minimizing loss of agent to outside spaces. Unclosable openings act as persistent leakage paths, so keeping their area as small as possible helps preserve agent within the protected zone and supports uniform distribution. This minimizes the rate at which agent bleeds into adjacent areas and maintains the effectiveness of the system. In practice, if openings can’t be closed, designers narrow them or add barriers, vestibules, or sealing strategies around them to reduce leakage. The other options would either increase leakage, ignore design considerations, or demand an impractical or unsafe level of sealing, so keeping the area to a minimum is the correct approach.