ESFR Sprinklers – The Perfect Solution To Warehouse Fire Protection? (Updated)

February 1st, 2017

Explore with us in this article the do’s and don’ts of using ESFR sprinkler systems. We discuss common pitfalls in applying these types of sprinkler systems and provide detailed explanations on their correct usage including applicable codes and regulations. Presented are the latest updates on this subject matter based on the 2013 and 2016 editions of NFPA 13, FM Global Property Loss Prevention Data Sheets, and relevant results from the latest fire tests with ESFR sprinkler systems.

Additional information on sprinkler application issues can be found in the article Sprinkler Protection Simplified.

ESFR (Early Suppression, Fast Response) sprinkler systems have been rightfully touted as one of the best solutions and best investments in warehouse storage. But are ESFR systems an all-inclusive solution to warehouse protection? Is it the “miracle cure” to all warehousing problems?

Not exactly. There’s a gamut of problems that may arise from a business owner unknowingly moving into a building equipped with an ESFR system. Let’s discuss these potential pitfalls in more detail by giving some specific examples.

Background – History

In the 1980s, early suppression, fast response (ESFR) sprinkler systems were developed as an alternative to in-rack systems. They were designed to actually suppress or extinguish the fire, while conventional sprinklers can only control fires, therefore eliminating the need for extinguishment by firefighters.

How do they work? ESFR sprinklers are designed to release 2-3 times the amount of water of conventional sprinkler heads and to emit larger droplets of water, which in turn have a greater momentum than droplets emitted from conventional heads. As a result, more water and a greater share of the water reaches the fire allowing the flames to be extinguished.


In general, ESFR systems can be used in warehouses with storage that do not exceed 40 feet in overall height, and with a ceiling height of less than 45 feet. And there are sprinkler system protection schemes that will allow storage above those heights. These may include in-rack sprinklers or a combination of ESFR with in-rack sprinklers.

ESFR systems are designed to protect a wide array of commodities. This provides more flexibility in warehouse operations when compared to control mode (conventional) sprinkler systems, which are designed to protect only the commodities that were stored at the time of system installation. If the storage situation requires in-rack sprinklers to be installed to the existing control mode systems of a warehouse building, often building owners prefer to change over to ESFR, simply because then there is no need to worry about damaging in-rack sprinkler heads during normal storage operations. Additionally, in-rack sprinklers have to be removed and sometimes replaced with each new tenant, since the tenants own the racks. Therefore, converting to an ESFR system is at times more cost-effective in the long run.

Here are some common questions asked about ESFR systems:

Question: Can smoke & heat vents be installed in buildings equipped with ESFR systems?
Answer: Yes. In the most recent edition of NFPA 13, the 2016 Edition, Section states “Early suppression fast-response (ESFR) sprinklers shall not be used in buildings with automatic heat or smoke vents unless the vents use a high-temperature rated, standard response operating mechanism.” However, jurisdictions where the International Fire Code have been adopted, unless local amendments are used to change the regulations, prescribe that smoke and heat vents are not required in buildings equipped with an ESFR system.
Question: Can draft curtains be installed in buildings equipped with an ESFR system?
Answer: No. Draft curtains/curtain boards can interfere with the way hot air moves at the ceiling (called ceiling jets), which is how most sprinklers including ESFR heads actuate/open. This change can result in failures of the ESFR system. It needs to be emphasized that sprinkler systems are the most critical means of protecting a warehouse. If the sprinkler in a warehouse fails, it typically results in a catastrophic failure of the entire fire protection system. Therefore, ensuring proper sprinkler system function should be of highest priority when compared to other protection systems such as draft curtains. If ESFR sprinklers are used next to conventional sprinklers, 2-foot curtain boards are required to separate the ESFR systems from the conventional sprinkler systems.
Question: Can ESFR systems protect all types of rack storage?
Answer: No. There is no one ESFR system available to protect all types of rack storage, rather there are several types of ESFR sprinkler heads and required water pressures, with each one of them to be applied in specific storage scenarios. It should also be noted that ESFR systems cannot be applied to open top containers. However, since the concern with open top containers relates to these containers retaining the water (like a reservoir) and not allowing the water to flow down to the lowest levels of a rack, there is no harm if open top containers are used in the lowest level of the rack (at or near the floor).

The most recent 2015 edition of DS 8-9 by FM Global states:

Open-top, five-sided noncombustible containers do not need special consideration when:
1) They are located on the top tier of the storage rack and all storage located below them is also in noncombustible containers, or
2) They are all located on the bottom tier of the storage rack, or
3) They are provided with either wire mesh siding or large uniform openings along the bottom perimeter of each container, such that all water that enters the container will leave the container at the same flow rate and discharge evenly into the flue spaces. For this option to apply, storage within the container cannot be water absorbent nor be capable of blocking any of the container holes, or
4) They are intermixed with storage in combustible containers, they are not located on the top tier of the storage rack and they do not extend into the transverse flue spaces.

Open-top, five-sided, combustible containers do not need special consideration when:
1) They are all located on the bottom tier of the rack storage, or
2) They are not located on the top tier of the storage rack and they do not extend into the transverse flue spaces, or
3) They are provided with either wire mesh siding or large uniform openings along the bottom perimeter of each container, such that all water that enters the container will leave the container at the same flow rate and discharge evenly into the flue spaces. For this option to apply, storage within the container cannot be water absorbent nor be capable of blocking any of the container holes, or
4) The storage racks are equipped with flat or domed-shaped fixed-in-place lids that are provided directly above the open-top containers and will prevent water from entering the open-top container, as well as distribute water equally into all flue spaces (this only applies for pallet loads that are fixed-in-place within a rack structure).

Question: Once an ESFR system is installed, can any business move in and store however they want?
Answer: No. Each type of ESFR sprinkler head can protect a different set of commodities. For example, based on the NFPA 13 standard, K-25 ESFR cannot protect cartoned expanded plastics, such as products that have >25% by volume of foam packaging in a cardboard box (FM Global Loss Prevention Data Sheet DS 8-9 does offer K-25 ESFR options for protecting cartoned expanded plastics. These FM protection schemes, however, need to be applied as alternative means of protection criteria to NFPA 13). For building owners or in warehouses, where the types of storage fluctuates, the best return for your ESFR dollar is the K-17 ESFR head, which protects a large variety of products, but still requires comparatively low water pressures.
Question: Are there instances where in-rack sprinklers are required, even when the building is equipped with an ESFR system?
Answer: Yes. There are several instances where in-rack sprinklers are required with an ESFR system. For example, in cases where solid shelves are proposed in the racks, in-racks sprinklers will be required. Additionally, close attention must be paid to the ESFR tables in NFPA 13, especially Tables,,, and for ceiling heights greater than 40 feet. Many of the ESFR options in these tables require in-rack sprinklers.

* NOTE: FM Global no longer uses the term “ESFR” however ESFR sprinklers are viewed as simply K-16.8, K-25.2, etc. sprinklers when applying protection tables in Data Sheet 8-9. Therefore if a business owner is moving into a building that is equipped with an ESFR, and exposed expanded Group A Plastics is planned for rack storage, the K-Factor of the head will be used to determine whether in-racks are required.

Question: Are sprinkler systems required below catwalks if the overhead system is ESFR?
Answer: In the past FM Global Loss Prevention Data Sheets were used as alternative means of protection/criteria to NFPA 13. This was acceptable to most jurisdictions. The previous editions of FM Global Loss Prevention Data Sheet DS 2-2 did not require sprinklers below catwalks if the catwalk system was greater than 70% open and no more than 10 feet wide. This allowance was specific to ESFR systems. However, with the release of the new FM Loss Prevention Global Data Sheet DS 8-9, the term “ESFR” has been completely eliminated. The new requirements for sprinklers below walkways have been modified to a more generic requirement that applies to all types of sprinkler systems. See FM Global Loss Prevention Data Sheet DS 2-0 for the allowances for locations where sprinklers need not be installed below walkways. In all cases, sprinklers are required below open grids if the open grid depth is greater than 1/2 inch. In other words, FM Global Loss Prevention Data Sheet DS 2-0, Section Exceptions 1-3 apply to open grids if the grid is 1/4 – 1/2 inch deep. Therefore in most cases since grids of walkways are approximately 3/4 inch – 1 inch deep, sprinklers will be required below walkways.
Question: Can ESFR protect Exposed Expanded Group A Plastics?
Answer: Yes, though previously exposed expanded Group A plastics stored in racks were not permitted to be used with ESFR systems that were based on the NFPA 13 standard (2013 edition and prior editions). Only FM Global sprinkler protection schemes could be used, through the application of “alternative means and methods” to NFPA 13. However, since the release of NFPA 13 2016 Edition, ESFR systems are now allowed to protect exposed expanded Group A plastics. Some of the requirements for these protection schemes are open (mesh) shelving and installation of vertical barriers, see Sections and for more detail. Required water pressures for storage heights up to 25 feet are 30 psi for ceiling heights up to 30 feet and 60 psi for ceiling heights up to 40 feet (12-head calculation). Storage heights up to 35 feet with ceiling heights up to 40 feet require 60 psi of water pressure. All protection schemes use K-25.2 ESFR sprinkler heads. Sprinkler head pressures of 60 psi almost always will require the use of a fire pump, which is an incentive to store only up to 25 feet.

For more information, see ESFR Protection Of Exposed Expanded Group A Plastics.

Question: Can I store products which are not protected by the ceiling level ESFR?
Answer: Yes, there may be circumstances that an existing ceiling level ESFR sprinkler system cannot protect some of the products stored in a warehouse. This is often the case if the ESFR system was specified for Class I-IV commodities, but some of the products stored in the racks are of higher hazard, e.g. rack storage of exposed Group A plastics. In these cases, new protection schemes prescribed in the 2016 edition of NFPA 13 allow the existing ceiling level protection to remain unchanged while protecting the racks with the higher hazard commodities with an ‘alternative protection’ scheme, see Sections (Class I-IV) and (Plastics and Rubber) for more detail. These Alternative Protection schemes applied to only a few racks (with the higher hazard) can be very cost effective in these situations. These schemes can also be used in combination with solid shelves on these ‘alternatively protected’ racks, but in these cases will require in-rack sprinklers at every level.
Question: I have K-14 ESFR sprinkler heads in my warehouse, is there a problem?
Answer: There are changes in the application and use of K-14 ESFR sprinkler heads for Class I-IV and Group A Plastics commodities in buildings with 40-foot ceiling heights. While K-14 sprinklers are still allowed for other ceiling height configurations, the 2013 and 2016 editions of NFPA 13:

  • Eliminate the use of K-14 ESFR at a minimum operating pressure of 75 psi storage of Class I-IV to maximum storage height of 20 feet and 25 feet in buildings with a maximum ceiling height of 40 feet, and storage of Group A Plastics (cartoned and exposed unexpanded) to maximum storage height of 20 feet, 25 feet, 30 feet, and 35 feet in buildings with a maximum ceiling height of 40 feet.
  • Existing systems with existing storage need not be retrofitted. However, if new high-piled storage permits are required and K-14 ESFR sprinkler heads were previously installed in buildings with a 40-ft ceiling height, then the latest codes and regulations will need to be applied. In other words, there is no “grandfathering in”.
  • K-14 ESFR (12-head calculation) at a minimum operating pressure of 90 psi is still available for rack storage in maximum ceiling heights of 45 feet when in-rack sprinklers are installed.

For more information, see NFPA 13 2013 Edition – ESFR Code Changes.

Question: Can ESFR sprinkler systems be used with solid shelving?
Answer: Yes, one of the biggest changes since the release of NFPA 13 2013 Edition and the protection of commodities on racks with ESFR is the allowance for ESFR sprinklers in combination with solid shelving! ESFR sprinkler are now allowed to protect racks with solid shelving if in-rack sprinkler protection is installed.

For more information, see NFPA 13 2013 Edition – ESFR Code Changes.

Question: Can ESFR sprinkler systems be used with ordinary or light hazard occupancies?
Answer: Yes, since the release of NFPA 13 2013 Edition, ESFR can now protect ordinary and light hazard occupancies, such as offices or manufacturing spaces in a building that is ESFR protected throughout. This situation may be encountered, if the warehouse (shell) building was designed and built out with ESFR sprinklers, but at a later time, say, office space was added, or existing office space was increased. In other cases, the space above offices may be dry walled in and cannot be easily accessed. In these circumstances changes to the ESFR system protecting the storage will not require changes to the (ESFR) sprinkler system protecting (existing) office space.

For more information, see NFPA 13 2013 Edition – ESFR Code Changes.

Question: The water demand of the proposed ESFR system is too high, what can I do?
Answer: While there are new ESFR sprinkler heads and technologies available that utilize lower water pressures and smaller nozzles (with a smaller K-factor), problems can still arise with a specific ESFR design and building locations, where the municipal water supply is inadequate. Given the dramatically worsening effects of Global Warming on the water supply of drought stricken areas (such as Southern California), alternatives have been developed that require less water than a typical ESFR system. Often these protection schemes require the application of one or two levels of in-rack sprinklers and horizontal barriers. In return, the water demand on the ceiling level sprinkler system is sharply reduced (typically by 30% to 50%). Perhaps most importantly, the latest fire tests have shown that protection of the highest hazard commodities, such as exposed expanded Group A plastics, with storage heights up to 35 feet may require only one level of extended coverage in-rack sprinklers and horizontal barriers based on an ESFR ceiling level protection with K-16.8 heads at 50 psi. This is not only a 40% savings in water demand when compared to an ESFR system without in-rack sprinklers, but will often eliminate the need for a fire pump!

For more information, see Next Generation In-Rack Sprinklers.

Question: What are common misunderstandings seen in application of ESFR’s?
Answer: Some of the critical pieces of information that is often miscommunicated between business owners, realtors, and fire departments will often result in the incorrect application of ESFR systems. Let’s list some of them:

Commodity: To business owners, the commodity is the product that they are selling (i.e. the valuable goods). To the fire department and what is needed to determine protection, a commodity is what can burn in the warehouse. This includes, product (i.e. the valuable goods), the packaging (foam/expanded plastics, etc.) and the pallet (plastic versus standard wood, etc.).

Clearance: To business owners and realtors, clearance defines how high they can physically store. Clearances are typically considered the distance from the floor to bottom of roof structures, such as trusses, etc. To the fire departments and code users, clearances are short for “sprinkler clearances” usually termed to describe the distance between the top of the storage to the sprinkler deflector.

Ceiling Heights: To business owners and realtors ceiling heights are again used to define how high they can physically store. Therefore, they consider this measurement distance below the roof trusses and in most cases at lowest point of the roof (if sloped). For the fire department, ceiling heights, when determining types and designs of sprinkler protection, is given by the measurement from floor to the bottom of the roof deck (or insulation) at the highest point. Incorrect selection of ESFR types and pressures can result from these types of misunderstandings.

Flue Spaces: Rack flue spaces are the required separation distances between rack loads that are governed primarily by the rack uprights. These spaces cannot be used to store any products and need to be maintained at all times. They allow the sprinkler water expelled by the ESFR sprinkler heads to reach and wet all sides of the rack (bays). ESFR sprinklers require transverse flue spaces. Transverse flues are the spaces between adjacent rack uprights or rack bays when looking side-to-side. If storage heights are larger than 25 feet, longitudinal flue spaces are required in addition to the transverse flues. Longitudinal flue spaces (running perpendicular to transverse flues) are the required separation distances governed by the rack uprights in the ‘rear’ of the (double row) racks. Oftentimes these longitudinal flues need to be protected by ‘pallet stops’. As the name suggests, these devices are installed to prevent the pallets from being pushed into the longitudinal flue (rear) space and blocking the water flow from the ESFR sprinklers.


While ESFR systems may solve many of the more challenging problems in warehouse protection against fires, ensuring that the correct type of ESFR is used involves full understanding of the commodity and methods of storage in the warehouse. Careful consideration must also be given on the long-term use and range of flexibility expected by the owner of the building.

Full communication between the fire department and business owner is necessary to ensure the terminologies used by each side is understood by the other party, as that can result in the incorrect ESFR types and/or pressures.

A final consideration as to whether additional ESFR heads should be required below catwalks merits additional testing.

Disclaimer: The content presented is for general information purposes only and does not constitute advice. Readers should not act upon this article’s content or information without first seeking appropriate professional advice.

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