NFPA 92 / IBC Section 909

NFPA 90A / NEC Article 725.3 / IBC 907.3

HVAC shutdown and smoke damper control on fire alarm must be accomplished through hardwired connections, not through BAS software commands alone. BAS software can supplement but not replace hardwired interlocks. If the BAS network fails, loses power, or has a software error, the life-safety interlock would not function. NFPA 90A requires direct hardwired shutdown independent of any programmable system.

NFPA 90A Section 4.3.10.3

Flexible duct is not permitted to penetrate fire-rated wall or floor assemblies. Only rigid metal duct with proper fire dampers may pass through rated barriers. Flex duct will burn through and compromise the fire barrier.

NFPA 90A Section 4.3.3

Duct insulation installed in a plenum space must have a flame spread index of 25 or less and a smoke developed index of 50 or less per NFPA 90A. A rating of 30 exceeds the maximum and creates a fire hazard in the plenum.

NFPA 92 Section 4.4.2 / IBC 1010.1.3

This passes code. NFPA 92 Section 4.4.2 requires stairwell pressurization to achieve two performance criteria: (1) a minimum pressure differential of 0.05 inches w.c. across closed doors (this system achieves 0.08), and (2) sufficient airflow through open doors to prevent smoke migration. The 200 fpm velocity through open doorways is commonly accepted as the minimum to prevent smoke infiltration. IBC 1010.1.3 limits door-opening force to 30 lbf — the measured 20-28 lbf is within limits. The system achieves the delicate balance between maintaining enough pressure to exclude smoke while not overpressurizing to the point where doors cannot be opened.

NFPA 92 Section 4.4.2.1

NFPA 92 Section 4.4.2.1 requires multiple injection points for stairwells exceeding 8 stories in height. A single injection point creates excessive pressure at the top and insufficient pressure at the bottom, resulting in inability to open doors at upper floors and inadequate pressurization at lower floors. Multiple injection points every 2-3 floors are required for tall stairwells.

NFPA 92 Section 4.4.2.2 / IBC 1010.1.3

NFPA 92 Section 4.4.2.2 requires a means of pressure relief when all stairwell doors are closed. Without a barometric relief damper, the stairwell overpressurizes, making doors impossible to open (exceeding the 30 lbf maximum door-opening force per IBC 1010.1.3). Relief dampers maintain pressure within the required 0.05 to 0.10 inches w.c. differential.