Performance Based Fire (PBF) wanted to determine how open doors impact the effectiveness of stair pressurization systems during fire events, particularly in high-rise buildings. Open doors can cause significant pressure fluctuations that compromise the system's ability to prevent smoke infiltration and maintain safe egress conditions.
The annex of NFPA 92 clarifies that doors propped open are in violation of applicable codes and beyond the design requirements for stair pressurization systems. This clarifies that it’s not propped-open doors that should be considered but rather doors opening and closing due to normal egress. PBF used advanced airflow modeling methodologies to evaluate and compare the performance between compensated and simple pressurization systems under normal fire and egress conditions.
Properly designed stair pressurization systems are essential for maintaining safe building evacuation during a fire, ensuring compliance with safety codes, and protecting occupants from smoke exposure. PBF designs stair pressurization systems based on the principle of simplicity. The performance between simple and compensated pressurization systems under normal fire conditions is reasonably similar. Compensated systems only limited the smoke movement into the stairs when considering propped-open doors. The benefits of compensated systems might not justify their added complexity, expense, and overall increased risk of malfunction.
Section 403.5.4, Smokeproof Enclosures, International Building Code
Section 909.20.5, Stairway and Ramp Pressurization Alternative, International Building Code
NFPA 92, Standard for Smoke Control Systems
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