How to Arrive at 2,000 sqft CMDA Design Area?

8/4/2026

I have a CMDA wet system, protecting solid-piled Group A Plastics storage. The storage height will be under 12 feet.

Under Section 21.3.3(a), I have been led to the density of 0.60 gpm/sqft in Column C, over a remote area of 2,500 sqft. The 2,500 sqft remote area is what's getting me; it seems cut and dry that in my situation, I am stuck there unless I have a closed storage array.

I wanted to verify against other people's interpretations: are there any other ways I am missing that would allow the area to be brought down to 2,000 sqft?

I primarily ask because I have seen other systems in the field with areas of 2,000 with densities 0.40, 0.50, 0.60, and I'm unsure of how those systems have gotten to that point with the current codes.

For clarity, I am using the 2022 edition of NFPA 13. Any input would be appreciated. Thanks.

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8 Comments

Pete H

8/4/2026 06:15:35 am

From the 2019 edition (you may have to update some reference numbers for 2022):

21.3 CMDA Sprinkler potection criteria for palletized, solid piled, bin box, shelf, or back to back shelf storage of plastic and rubber commodities.

21.3.5 For storage of Group A plastics between 5 ft and 12 ft in height, the installation requirements for extra hazard systems shall apply.

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19.2.3.2.7 Extra Hazard Occupancies
19.2.3.2.7.1 For extra hazard occupancies with ceilings not exceeding 30 ft in height, the system area of sprinkler operation shall be permitted to be reduced b 25 percent without revising the density, but not to less than 2000 sq. ft. where one of the following conditions occurs:
1) High temp sprinklers are used
2) K11.2 sprinklers or larger are used.

Brett

8/4/2026 08:28:22 am

Those references from chapter 19 do not apply to OP's situation since their storage is not classified as an EH1 or EH2 hazard. Section 21.3.3.1 says that the area can only be reduced where either:

1) Table 21.3.3(a) says "EH1" or "EH2" and you use K-11.2 sprinklers or high temperature sprinklers.
2) Closed array storage.

Anonymous

8/4/2026 10:24:38 am

I interpreted 21.3.5 as referring to sprinkler spacing criteria, specifically Table 10.2.4.2.1(c), as 10.2.4.2.1(d) is spacing criteria for High-Piled Storage, which Chapter 3 defines as storage >12ft in height.

If it wasn't for 21.3.5 allowing the use of the Extra Hazard table, there would be no direction for spacing requirements on storage between 5 and 12 feet, but I don't think it allows you to call it Extra Hazard for the purpose of reducing the remote area below what is said in Chapter 21.

Dan Wilder

8/4/2026 07:57:13 am

Hasn't changed in the 2022 but there are now 2 separate sections to clarify that either condition allows the reduction
19.2.3.2.6 - High Temp Sprinklers
19.2.3.2.7 - K-11.2 or greater

Franck

8/4/2026 11:16:21 am

They have been using the miscellaneous table for storage up to 12 ft of group A plastic and ended up with the adjustments indicated avove.

But you should not consider it as an acceptable solution as these adjustments apply only for extra hazard occupancies. In your case, you are using the design equivalent to an EH Gr 2, but cannot use the adjustment that are only applicable for an occupancy and not for a commodity

Another explanation might be that they made the evaluation for a class IV commodity with a higher height of storage where the area of application is 2000 sq ft.

Jack G

8/4/2026 12:41:54 pm

Start with the hazard classification curve and take all the reductions like qr heads.
Then per chpt 21 apply reduction for high temperature heads and / or closed array storage. Should come up with a 2000sqft MRA.

8/4/2026 12:44:58 pm

You should check the MeyerFire cheat sheet for area reduction from I think May of 2022 or so. That may help also

8/4/2026 01:00:05 pm

I have looked at the cheat sheet, the only note it has about remote area minimums for storage is to look at NFPA 13 for if High Temperature sprinklers may make a difference, on note 4 on the right.

Storage doesn't come with quick response reduction, and for Solid-Piled, you're only allowed high-temp(or high k-factor) reduction if your commodities density falls in accordance with EH1 or EH2 according to table 21.3.3(a).

How to Arrive at 2,000 sqft CMDA Design Area?

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