Can ESFR Be Used for Extra Hazard Group 2?

2/8/2023

I have a situation where I need to protect a modular home manufacturing facility.

It has a paint both that's self-contained with its own sprinkler hookups, all the regulars of a tiny home making shop basically. They will have rack storage of wood products up to 20' high and wanted the design to be such that they could move the storage rack locations in the future if they wished.

NFPA 13 (2016) A.5.4.2 gives a list of some Extra Hazard Group 2 occupancies and it specifically lists (4) Manufactured home or modular building assemblies (where finished enclosure is present and has combustible interiors) I had made the assumption that ESFR was a worst case, safe bet design for the entire facility due to the amount of water you get from heads opening up.

The contractor is concerned with how code says one thing in one place and something open to interpretation in another place. Section 8.4.6.6 says "ESFR sprinklers designed to meet any criteria in Chapter 12 through Chapter 20 shall be permitted to protect light and ordinary hazard applications."

That's fine, but I just see that as just a statement.

When you get to the requirements for Storage, Section 12.6.7.1 says the following: "ESFR sprinklers designed to meet any criteria in Chapter 12 or Chapter 14 through Chapter 20 shall be permitted to protect any of the following: (1) Light hazard occupancies (2) Ordinary hazard occupancies (3) Any storage arrangement in Chapter 13 referencing OH1, OH2, EH1, and EH2 design criteria"

Item 3 is where I want to make the argument that we can in fact use ESFR sprinklers in an Extra Hazard Group 2 scenario.

Can ESFR be used for an Extra Hazard Group 2 situation like this?

I need some expert opinions/interpretations. Thanks in advance.

Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe

13 Comments

Dan Wilder

2/8/2023 07:45:30 am

Hoping to learn from this one but my thoughts...

I don't see a correlation between an EH design and the Storage Chapters to apply an ESFR design criteria? The allowance for Light & Ordinary designs with ESFR came more from storage buildings being designed with ESFR sprinklers and then having offices move in and not requiring a change out of sprinklers (Need to look in the meeting notes from 2013 when the text changed going into 2016).

I think that the shielding created by the buildings in construction below would exceed a typical calculation area of an ESFR design (4x3). ESFR also isn't allowed with solid shelf storage without additional protection in place. As you stated, the amount of water from an ESFR sprinkler would seem to be enough for an incident however this also can be a hinderance when more sprinklers open and the water supply is exceeded.

Most of the ESFR storage sprinklers I quick checked have no mention of Extra Hazard and are specific to different criteria within the storage chapters, but other large K-Factor sprinklers (CMDA K25 sprinklers) do list EH as an option per NFPA 13 criteria.

Glenn Berger

2/8/2023 08:14:30 am

In addition to the excellent statements made by Dan above, I recommend contacting various mfg of ESFR sprinklers as the allowable conditions do differ. With that said, you did not provide any information on the building construction for which you are protecting. That is another variable that needs to be considered.

Mike Morey

2/8/2023 08:16:57 am

As Mr. Wilder stated, the allowances to protect "occupancy group" designs with ESFR is limited to LH and OH. The later reference in the storage chapters is specifically for Low Piled/Misc storage and any other storage occupancy in the storage chapters that calls out an occupancy group protection scheme as being sufficient. Manufacturing and similar extra hazard facilities differ greatly in their fire loading and development and were not contemplated when ESFR was extended to protect other occupancies. As mentioned, LH and OH were added for ESFR warehouses with office, break, restroom, mechanical room, etc occupancies peppered throughout with and without ceilings to be protected without having to remove and replace ESFR sprinklers that would clearly put out a fire in those scenarios. It also helped ensure Shell/TI buildings were fully sprinklered at final inspection rather than owners trying to convince AHJs to accept wait and see on office shell areas etc.

Anthony

2/8/2023 08:29:21 am

ESFR isn't a better sprinkler it's a specific sprinkler. If NFPA 13 calls out EH2 specifically then you need to engage with your AHJ at a minimum. ESFR is specifically designed and tested for storage arrangements not open floor space and manufacturing.

There are 2 differences between EH2 and ESFR.
EH2 will have a remote area 2x larger and hose stream 2x larger.

Here's my best go though:

ESFR will have an effective density that's 2x (or more) as large.

eg: K25.2 @15 psi = 97.6 gpm --- over 100 sqft = 0.976 gpm/sqft

Total minimum flow for EH2 + 0.4gpm/sqft * 2500 sqft = 1000 gpm

Total minimum flow for our example: 12 head s* 97.6 gpm = 1171 gpm

You could argue the stringent installation obstruction requirements, total greater volume of design flow and increased per head discharge would make for a reasonable acceptable approach of using ESFR over EH2. If there is storage there already, you could extend the storage system over the production area without the use of draft stops for one contiguous system.

I, however, would not make this argument. Simply because you cannot properly classify which ESFR discharge criteria you are working with. Building height is easy, obviously, but the commodity class and storage height is hard not nonexistent for your case.

I'll end where we started: ESFR isn't a better sprinkler it's a specific sprinkler.

Jesse

2/8/2023 08:34:40 am

ESFR is a completely different design approach. So whereas, NFPA 13 allows ESFR to be used in OH2 occupancy hazard class areas, its doesn't for EH.

The sprinkler is the other issue. I'm not aware of any ESFR sprinklers listed for EH areas.

Casey Milhorn

2/8/2023 08:54:11 am

I think I'm in agreement with everyone. If you are the EOR for this project, I would be hesitant to make the assumption that ESFR's are equivalent. If you are the fire protection contractor, I would DEFINITELY not make this leap.

If you are the EOR and have the resources and time, I would investigate any fire testing that was done on mobile home production (I would imagine there has to be some out there). Even though tiny houses are somewhat of a new trend, especially building them in interior production facilities, mobile home construction has been around for 60+ years. Some of these units can be up to 2000 sqft or more, but if I had to guess typically are never more than 1000 sqft per "half". The production process and materials used should be very similar. I would also want to know how close in proximity they are being stored to each other, and on the other end how the raw materials are being stored (where ESFR might be the correct call).

I would think separation of the finished units would be key here as to give the roof system a chance to activate before the fire could spread to additional units. These tiny houses would do a great job of shielding the fire from the sprinkler system, giving a chance for the unit to become fully engulfed. If a case could be made that units were adequately separated, then ESFR might be the correct call to allow for future modifications to the assembly/storage areas.

Just my two cents and I would definitely get some additional insight from someone that has experience in protection of mobile home or tiny home manufacturing.

One last thing, just because someone has a great idea on how to manufacture or store something, doesn't mean there is a correct/adequate solution from the fire sprinkler industry. Sometimes the owner just needs to stop and change the way they want to do things, or get everyone to accept the increased risk which is rolling the dice for everyone involved.

Great question!

Brad K

2/8/2023 09:00:32 am

Interesting question. One consideration when comparing OH/EH design density with ESFR calculations. Recall that Quick Response / Fast Response elements are not permitted for use with Extra hazard occupancies. Ref 2019 NFPA 13-10.2.3 and 19.3.3.2.2.2. Perhaps arguments can be made either way since 10.2.3 mentions density/area design method. This could become a sticking point in negotiations.

SAFPI Sebastian Stecyk

2/8/2023 09:12:27 am

In my opiniom, IT is not possibile.
Acc. with point 19.3.3.2.2.2 and 10.2.3 od the NFPA 13 is not permitted to use QR sprinkler.

RTI of the QR sprinkler is below 50 and the same or very similar like ESFR.
Regards

2/8/2023 10:37:42 am

While I think the advice here is pretty much on the side of ESFR protection and Extra Hazard are different hydraulic designs, I do have a recommendation.

I would design the piping system so that way the lines and mains can handle both the EH2 and ESFR situations hydraulically, along with using the more stringent ESFR installation criteria for obstructions. Depending on the sprinklers to be used, I would install 3/4" or 1" outlets (and maybe use 1" outlets with 3/4" bushings) in the pendent position so the only modifications in the future would be to swap out sprinklers assuming the right elevations for the different deflector requirements can be work on site. Most sprinkler manufacturers provide a pendent version of their extra large orifice sprinklers. The same can be done with uprights, but the upright ESFRs are not always allowed in all storage arrangements.

Jonathan Worden

2/8/2023 10:43:53 am

Great question! Definitely learned something myself on this one. I, like many others probably immediately assumed more water = ability to protect higher hazard. It appears it's not that straight forward.

I think the key word here is "storage"... (3) Any storage arrangement with OH1, OH2, EH1, and EH2 design criteria.

While the type of occupancy you described may be EH2, it is not storage. Think of it more in terms of arrangement of commodity and less in terms of what's actually burning. NFPA storage standards are based on full scale fire test and past loss fires. A number of factors go into developing the standards related to storage such as commodity class, storage arrangement, storage height, clearance from top of storage to sprinkler just to name a few.

With the occupancy you described (manufactured home or modular building assemblies), you will certainly have shielding of combustibles. NFPA 13 recognizes this as severely impacting the performance of ESFR sprinklers.

The following was taken from NFPA 13 (2022) Section 23.1.1 Commentary:

Systems protecting extra hazard occupancies are specifically left out of this discussion because ESFR sprinklers are not permitted to be used in systems protecting extra hazard occupancies due to the potential for shielding of combustibles. Many extra hazard occupancies have equipment or construction that will shield the combustibles from any fire sprinkler discharge at the ceiling/roof. ESFR sprinklers are not designed to protect hazards where the combustibles are shielded. Therefore, extra hazard occupancies have been specifically left out of the list of permissible ESFR uses.

ESFR sprinklers are also permitted to be used for the protection of storage arrangements requiring protection as an ordinary hazard Group 1 (OH1), ordinary hazard Group 2 (OH2), extra hazard Group 2 (EH1), or extra hazard Group 2 (EH2) design under the provisions of Chapter 4. While the design criteria for EH1 and EH2 are quite similar to that prescribed for extra hazard occupancies, these storage applications under Chapter 4 would not include a shielding hazard as might be the case with other extra hazard occupancy designs.

Cheers!

Sebastian Stecyk

2/8/2023 11:28:07 am

I found in NFPA 13 some additional information regarding use ESFR sprinklers in EX1 i EX2 hazard. You can also see point 14.2.7 and point 23.1.1 - NFPA 13, edition 2022,
Especially additional comments in Handbook of the NFPA13 for 23.1.1 point is very important.
I think that is problem with protection of flammable liquids and materials with similar properties and occupanncy defined in EX1, EX2 or shielding hazard.
Acc. to 23.1.1. point, ESFR sprinklers could be used in storage arrangement under Chapter 4 if you have classification EX but only for storage area.

Franck

2/8/2023 02:58:15 pm

ESFR are specific sprinklers (as indicated above) to suppress fire over a small area with storage occupancy.
They are not designed to control a fire for a process occupancy.
As stated above, small less hazardous occupancy in a storage area is acceptable, but this is not your case.
Too many possibilities to open more ESFR than the design and overtax your system.
A simple sketch would show you how it works for the requirement of 12 ESFR. If the fire starts in the center of the rectangle made by 4 ESFR, you may expect to open the 4 of them. And if the fire extends a bit beyond, you will open the second rows, resulting in… 12 sprinklers (not 16 as you consider an expansion as a circle from the start point).
Now, if there is any condition that could require the opening of sprinklers beyond this “second row”, your fire is out of control…
This is also why they need to be fast operating : suppress the fire as soon as possible, don’t open sprinklers beyond…

Chris

2/13/2023 10:17:59 am

I agree with basically everyone else, ESFR's are only for storage applications, so if you have an area that isn't storage and is EH you cant use ESFR in that area, and I would say it also needs to be in a separate compartment from the ESFR's so you are not mixing SR with QR/FR.

Can ESFR Be Used for Extra Hazard Group 2?

Leave a Reply.

ALL-ACCESS

SUBSCRIBE

COMMUNITY

YOUR POST

PE EXAM

FILTERS

ARCHIVES

PE PREP SERIES