Please help me above how much height, do we need to provide stair pressurization system. If not height, which decide the need fpr stair pressurization system as per NFPA.
NFPA standards does not require stairwell pressurization. It does requires stairwells in air traffic control towers, existing high rise apartment buildings without sprinklers and other very specific situations in very tall buildings be smokeproof enclosures.
The requirement for the installation of stair pressurization systems will be dictated by your locally adopted model building and fire codes. Here in the City of San Antonio we are under the 2015 Edition of the International Family of Codes (International Building, Fire, Existing Building, Plumbing, Mechanical, Energy Conservation, Zoning, etc. Code). These codes require high-rise occupancies (defined in these codes as an occupancy in which the deck of the uppermost occupied floor is greater than 75 feet above the lowest level of fire department vehicle access) required interior exit stairways to be smoke proof enclosures with stair pressurization offered as an acceptable method of achieving that goal (alternative).
Again it depends on your locally adopted codes and standards.
Hopefully that helps.
Bob Gobert, SET
I hope to answer your question by providing the NFPA codes and standards. A building where the floor of an occupiable story is greater than 75 ft above the lowest level of fire department vehicle access has provisions in Section 11.8 of the 2018 NFPA 101. Referring to 18.104.22.168 all vertical exit enclosures serving a building with an occupiable story as defined above shall have enclosures in accordance with 22.214.171.124. The exit enclosure has alternate performance designs for creating an enclosure to limit the movement of products of combustion from a fire. The design method is to provided a system by using natural ventilation, by using mechanical ventilation incorporating a vestibule, or by pressurizing the enclosure. Consult with Section 126.96.36.199.1 of NFPA 101 for the system design requirements for enclosure pressurization. Reading this section the user will find the pressurization is to be in accordance to NFPA 92.
The code user should always consult with the subsection _.4 of the occupancy chapters to verify no exceptions, restrictions, or additional requirements apply.
Let me know if this helps.
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