Ordinary Hazard Group 2 Limit Storage to 12-ft?

4/16/2024

We have an existing manufacturing area subject to NFPA 13-2022 Edition.

The Ordinary Hazard Group 2 manufacturing area sprinkler system can meet Figure 21.2.2.3.2 requirements for 0.20 density over 2,200 SF plus 500 GPM for hose streams required for Class III storage to 20 ft. high.

Does the Ordinary Hazard Group 2 requirement of Section 4.3.3.2 (2) still limit storage height to 12-ft, regardless, since this is not a dedicated storage area?

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5 Comments

Pete H

4/16/2024 07:14:38 am

If you have 20'-0" high class III storage, the hazard classification isn't ordinary hazard group 2, it's High-Piled storage.

NFPA 13 (2022 Edition)
4.3.6. High piled Storage. Storage arrangements that do not meet the requirements of 4.3.1.4 through 4.3.1.8 shall be protected in accordance with chapters 20 through 25.

4.3.1.4 Miscellaneous Storage
4.3.1.4.1 Miscellaneous Storage shall not exceed 12 ft. in height.

So you're not miscellaneous storage.

4.3.1.5 Low Piled storage
4.3.1.5.1 Low-Piled Storage of Class I through Class IV commodities shall not exceed 12 ft in height

So that's out.

4.3.1.6 Miscellaneous Tire Storage
Nope.

4.3.1.7 and 4.3.1.8 are protection criteria for Miscellaneous and Low-piled storage, which cuts at 12'-0".

So you go to chapters 20 through 25.

Which you did, you're manufacturing area was calculated to high piled storage for class III and high temp sprinklers. 2200 sq. ft at 0.2 with 500 hose.

The hazard classification is based on the highest hazard in the area, which is the storage classification, not the ordinary hazard classification. So it doesn't matter about what ordinary hazard limits are, you calculated the area as high-piled storage.

Glenn Berger

4/16/2024 08:11:50 am

The answer to your question concerning storage height in an OH2 sprinkler system is yes.

You have the delicate balancing act of ensuring that the actual occupancy and use of the space is appropriate for the design criteria of the sprinkler system chosen.

Jesse

4/16/2024 08:12:41 am

0.20 / 2200 isn't an OH2 density. But it is a density consistent with High Piled Storage. Whereas the manufacturing is OH2, the design density driver is the storage, and at 20-ft, this isn't misc. storage.

Chris

4/16/2024 09:11:02 am

The density is the same, but the classification is very different between OHII and HPS. Others are elaborating on many of these, but the one thing that can be added is that normal sprinklers are not rated for storage. If you use a typical K8.0 or K11.2, it usually isn't listed for use in High Piled Storage applications. You must find a storage-rated sprinkler, usually starting at K11.2. I believe that these calc the same as a normal head, just cost a small amount more. I assume they have some unique feature that makes them better at fighting storage fires than a traditional sprinkler? Somebody please add to this if able!

Richard

4/16/2024 10:03:24 am

Thank you Pete H for the way you broke it down.

I will treat it as a high piled storage area with some incidental OH2 operations instead of an OH2 operations area with incidental high-piled storage - brilliant!

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Ordinary Hazard Group 2 Limit Storage to 12-ft?

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