NFPA 90A / NEC Article 725.3

NFPA 90A / ASTM E84

This installation is compliant. NFPA 90A requires that duct insulation materials have a flame spread index of 25 or less and a smoke developed index of 50 or less when tested per ASTM E84 (Standard Test Method for Surface Burning Characteristics of Building Materials). At 20 flame spread and 45 smoke developed, this insulation meets both thresholds. These limits are especially critical in plenum spaces where fire and smoke can spread rapidly through the return air path.

NFPA 90A / IMC Section 606.4 / high-rise office Mechanical Specification

This firestat installation is code-compliant. The 125 degrees F trip point in the return air stream is consistent with the high-rise office specification and NFPA 90A requirements for high-temperature cutout. The hardwired connection to the fan disconnect ensures the safety function operates independently of any BAS software. If return air temperature exceeds 125 degrees F, it indicates a fire condition in the occupied space, and immediate system shutdown prevents the HVAC system from spreading smoke and hot gases through the ductwork to other areas of the high-rise.

NFPA 90A / NEC 725.3

Duct smoke detector shutdown must be hardwired directly to the AHU disconnect or starter, independent of the BAS. A BAS software command alone is not acceptable for life-safety shutdown because software can fail or be overridden.

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.