Sprinkler Req'd in Open Air Chamber Enclosure?

7/8/2021

We have a project with a generator room on the outside of a building. There is a large louvre to an air chamber that is about 8-feet wide before another concrete wall is to be erected. The concrete wall has some bracing back to the main building.

Is there a reason sprinklers should be required in this air chamber that is open to the sky?

I'm looking for code help either way. Thanks in advance.

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3 Comments

Mike

7/8/2021 08:16:05 am

If it's open to the sky, how will you get the heat to accumulate and then actuate the sprinkler?

Dan Wilder

7/8/2021 09:00:45 am

This sounds no different than a make up air shaft we see on enclosed or underground parking garages with the metal grating at the top to prevent people from falling in (if there is even that much protection at the top).

As Mike stated, there is no heat collection and this is (by what I am gathering) a mechanical shaft. You may have a requirement to place something at the bottom if the shaft is considered "accessible".

NFPA 19' 9.2.11 - Noncombustible Vertical Shaft
NFPA 19' 9.3.3 - Vertical Shafts

Todd Wyatt

7/8/2021 09:18:20 am

The applicable Building Code (e.g. 2021 IBC) will determine where an "approved automatic sprinkler system" (AASS) is required and where it is exempt from being installed. The referenced standards (e.g. NFPA 13) includes the "hows" for the design, installation, testing, and maintenance for AASS, but not necessary the "where."

2021 IBC Section "903 Automatic Sprinkler Systems" discusses these requirements. "903.2 Where Required" identifies by Occupancy Classification (OC) where an AASS is required. The Design Team may have included an AASS for an OC that does not require an AASS for other reasons (e.g. allowable area increase).

The example you provided, without seeing drawings, could be interepreted in several ways to argue for not providing an AASS for this space. This "air chamber", if not physically attached to the building, could be classified as a separate "building" and assigned an OC that does not require an AASS. The IBC definition of "building" is "any structure utilized or intended for supporting or sheltering any occupancy." The definition for "structure" is "that which is built or constructed." Because of these "vague" definitions, most AHJs require all "buildings" and "structures" to be assigned an Occupancy Classiciation, even somehting like this "air chamber".

The other option is to have the AHJ review the "air chamber" and provide an interpretation if it requires an AASS based on its hazard and mitigating conditions (e.g. open to air above).

The Codes cannot foresee every special situation so it gives the AHJ some opportunity to rule on these special situations. Understand though, AHJs are cautious in permitting a situation that could cause health, safety, and welfare issues so they are typically very conservative in their interpretations.

Sprinkler Req'd in Open Air Chamber Enclosure?

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