NFPA references are based on current editions. While NFPA 101, Section 30.3.1.1.4 (New Apartments) allows vertical penetrations to be protected with a 1-hour rating when sprinklered, NFPA 101, Section 30.5.2 requires HVAC equipment to comply with NFPA 90A.
According to NFPA 90A, Sections 9.1.3 and 6.8.3, a higher level of protection is required for shafts that penetrate more than four floors (2-hr fire rated and fire dampers). Does the exception provided in NFPA 101 permit reducing the required fire rating to 1-hour for duct shafts, or does NFPA 90A take precedence? I'm curious to hear different perspectives on this. I can understand both sides of the issue but find it challenging to justify allowing a 1-hour fire rating for a vertical exit within a New Apartment while requiring a 2-hour fire rating for the duct shafts. Thanks in advance. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe
9 Comments
Christopher Nelson
1/21/2025 08:22:05 am
I would say this is similar to other situation where this accounting for building construction rather than stories. NFPA 101 7.1.3.2.1 requires exits 4 or more stories to be 2 hrs unless and existing building which you are not.
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Ricardo Gonzales Jr
1/21/2025 08:45:50 am
If both NFPA documents are adopted by the jurisdiction, most AHJs would use the more stringent of the two. Note the 1st word of the sentence above. It also depends on the AHJ on which department owns the building and its ratings vs. a single department responsible for it all. If it's compartmentalized, it could be the responsibility of the Mechanical, Architect or Fire Life Safety.
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Pete D
1/21/2025 09:18:48 am
I'd like to echo this with caution. NFPA 101 is not adopted by all jurisdictions, and it differs from IBC. I also want to comment, if your structure is IA, as classified by Table 601 IBC and the jurisdiction is on IBC, you have a 2 hr slab rating. The vertical duct can be "shafted", which I guess is jargon/vernacular for wrapped in fire rated material to carry the rating for the slab up to the next slab. That could mean 2 layers of 5/8 type X gypsum on a minimum 3 5/8 stud wall with base of wall and head of wall fire stopping, or a 2-hr shaft wall around the duct. Typically, we're cladding the duct for aesthetics anyway. I caution that the devil is in the details. You need to ensure for a conventional wall you're using UL, cUL, or Intertek or some listing agency recognized by your jurisdiction. My last comment is, in IA construction the slab penetration must have a T, F, and L rating. Understand the difference. It must block fire, temperature increase, and the leakage of air/smoke. Fire dampers come in 1.5 hr and 3 hr, and you will use the 90 minute fire/smoke damper for the 2 hr rating. They make butterfly dampers that are inside the duct beneath the slab penetrations that operate on mechanical links and torsion springs. These are ideal if it's a bulk run of duct without any branch offs. Otherwise, if the duct is wrapped in fire-rated material, any tributaries that branch off on the intervening floors will need fire-smoke dampers, which require mechanical actuation of the fire component and electronic actuation of the smoke component with a duct detector installed within 5 feet of the damper.
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Todd E Wyatt
1/21/2025 09:08:17 am
If (only) NFPA 101 Life Safety Code - 2024 (LSC) is the adopted, scoping Code for this Project, LSC takes precedence over Referenced Publications per Chapter 2 :
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1/21/2025 09:41:26 am
The NFPA design standards appear to be driven by IBC building classifications. For wood Apartments its primarily Type VA & VB (4 stories or less) & Type IIIA and IIIB 5 stories of wood.
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Jose R Figueroa
1/21/2025 11:57:43 am
The difference comes down to how NFPA 101 and NFPA 90A approach safety. NFPA 101 offers a bit more flexibility—if you install sprinklers, you might be able to reduce ratings a bit. On the other hand, NFPA 90A takes a stricter stance when it comes to HVAC shafts because they can quickly spread fire and smoke between floors. It's all about finding the right balance for fire & life safety. Consult your AHJ.
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Jose R Figueroa
1/21/2025 12:42:58 pm
I must include NFPA92 in the discussion. The HVAC system should also be a smoke control system. The HVAC system should be built according to NFPA 90 and 92. It will meet NFPA 101 requirements automatically.
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Wes
1/21/2025 12:48:38 pm
An HVAC system for a four story building does not automatically become a smoke control system under NFPA 92. A smoke control system is far more involved than an HVAC system.
Jack G
1/21/2025 12:27:09 pm
Assuming it is not HT construction or roof is not 20 ft higher than the floors.
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