CMDA, CMSA for 12-ft of Storage with 25-ft Roof?

9/29/2023

We have storage of Class I-IV commodity, in racks, with maximum distance from floor to top of storage of 12-ft with 10-ft aisles and roof deck at 25-ft.

The AHJ correctly asserts that this storage is not incidental to the occupancy and therefore cannot be considered as "miscellaneous storage".

Is there a way that these racks can be suppressed with roof-only sprinklers, preferably CMDA or CMSA?

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9 Comments

Alex

9/29/2023 07:14:07 am

Yes, you can get away with ceiling only protection using CMDA - NFPA 13 (2013) Table 16.2.1.3.2

Pete H

9/29/2023 07:28:21 am

It's not miscellaneous storage.

But it's not high-piled storage either.

It is "Low Piled Storage" ... a term rarely used and frequently confused with Miscellaneous storage. And a term that applies to all the storage configurations found in NFPA 13 (2016) Table 13.2.1 "Discharge criteria for miscellaneous storage" (but still applies to your low-piled storage as per Section 16.2.1.2.1.)

Anyway, you can do ceiling only protection with cmda sprinklers for this.

And if you convince them to limit their class iv commodity to less than 10'-0" from the floor (so make these bottom shelf items), you can even do OH2.

Glenn Berger

9/29/2023 08:08:23 am

I concur with the opinion that opinion that you do not have miscellaneous storage.

Based on the condition stated you most likely can use ceiling-only sprinklers. You need to go through the many tables concerning storage and pick the most suitable condition that is applicable. Make sure that you are giving the owner some leeway to modify the initial storage configuration.

Casey Milhorn

9/29/2023 09:58:40 am

I agree with everyone. You probably have low piled storage and will follow those guidelines. You will have to go through the different options to compare CMDA, CMSA, ESFR, etc. Keep any group A plastics below 5', Class IV below 10', and you will be at a very reasonable demand.

Randy rathert

9/29/2023 10:24:51 am

Im still learning here, so can you explain what OH2,EH2,and EH1 are?

Joe Meyer

9/29/2023 10:44:08 am

Hi Randy -

These are Ordinary Hazard Group 2 (OH2), Extra Hazard Group 1 (EH1) and Extra Hazard Group 2 (EH2).

Based on the question I would highly encourage you to get into some fundamental resources, like NFSA's Layout Book (https://nfsa.org/layoutbook/) or get into some fundamentals training as this is a very important and very fundamental topic.

All the best!

Jesse

9/29/2023 12:35:03 pm

Absolutely you can protect with CMDA ceiling only. Just pick a point on the design curve for protection of C-IV without IRAS

AB link

10/2/2023 08:30:37 am

I agree with the points made earlier.

To delve deeper into your fire protection strategy, here's a business-savvy approach:

You can opt for ceiling-only protection by employing CMDA (Control Mode Density Area) sprinklers for this storage configuration, aligning it perfectly with your specific fire protection requirements.

Adding to this, consider this strategic perspective: If you can successfully advocate for the Class IV commodities to be kept below 10 feet from the floor, essentially positioning them as bottom-shelf items, you open up the possibility of implementing OH2 protection.

Quentin M Maver

10/4/2023 10:52:07 am

HIGH-PILED COMBUSTIBLE STORAGE. Storage of
combustible materials in closely packed piles or combustible
materials on pallets, in racks or on shelves where the top of
storage is greater than 12 feet (3658 mm) in height. Where
required by the fire code official, high-piled combustible storage
also includes certain high-hazard commodities, such as
rubber tires, Group A plastics, flammable liquids, idle pallets
and similar commodities, where the top of storage is greater
than 6 feet (1829 mm) in height.

From NC IFC

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CMDA, CMSA for 12-ft of Storage with 25-ft Roof?

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