ESFR (Early Suppression, Fast Response) sprinkler systems have been rightfully touted as one of the best solutions and best warehouse storage investments. 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, eliminating the need for extinguishment by firefighters.
How do they work?
ESFR sprinklers are designed to release 23 times the amount of water of conventional sprinkler heads and emit larger water droplets, which have 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, warehouse owners can use ESFR systems in warehouses with storage that do not exceed 40 feet in overall height and with a ceiling height of fewer 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 originally 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 they own the racks. Therefore converting to an ESFR system is, at times, more cost-effective in the long run.
In the most recent edition of NFPA 13, the 2010 Edition, Section 188.8.131.52 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.
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 the highest priority 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.
ESFR cannot be applied to racks with solid shelving, except as specified for high bay record storage as indicated in NFPA 13, Section 20.7. Furthermore, 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).
Once an ESFR system is installed, can any business move in and store however they want? Well, it is a good question. The answer is No. For example, with one exception (NFPA 13, Table 15.4.1), ESFR systems cannot be applied to the storage of exposed (uncartoned) expanded Group A Plastics. Also, each type of ESFR head can protect a different set of commodities. For example, K25 ESFR cannot protect cartoned expanded plastics (such as products with>25% by volume of foam packaging in a cardboard box). Additionally, most furniture warehouses run into difficulties in protecting products with an ESFR system because of their rack storage of exposed expanded plastics. Exposed expanded include mattresses, pillows, synthetic foam packaging (nonstarch based), etc. For building owners or warehouses, where the types of storage fluctuate, the best return for your ESFR dollar is the K17 ESFR head, which protects a large variety of products, but still requires comparatively low water pressures.
There are many instances where in-rack sprinklers are required with an ESFR system. For example, in cases where exposed expanded Group A plastics (e.g. mattresses) on racks are proposed, the protection of these products are outside the scope of NFPA 13. FM Global does require racks to protect these products in most cases, even with an ESFR* system at the ceiling. Additionally, close attention must be paid to the ESFR tables in NFPA 13, especially Tables 184.108.40.206, 220.127.116.11, 18.104.22.168, 22.214.171.124 and for ceilings greater than 40 feet. Many of the ESFR options in that table require in-rack sprinklers.
* NOTE: FM Global no longer uses the term “ESFR”; however, ESFR sprinklers are viewed as simply K16.8,
K25.2, etc. sprinklers when applying protection tables in Data Sheet 89. Therefore if a business owner was moving into a building equipped with an ESFR and exposed expanded Group A Plastics is planned for rack storage, the head's KFactor will be used to determine whether racks are required.
In the past, FM Global 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 Datasheet 22 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 new FM Global Data Sheets 89, the term “ESFR” has been eliminated. The new requirements for sprinklers below walkways have been modified to a more general requirement that applies to all types of sprinkler systems. See FM Global 20 for the allowances for locations where sprinklers are not required 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 20, Section 126.96.36.199.3 Exceptions 13 apply to open grids if the grid is 1/4 – 1/2 inch deep. Therefore in most cases, since walkways are approximately 3/4 – 1 inch deep, sprinklers will be required below walkways.
Some of the critical 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 they are selling (i.e. the valuable goods). To the fire department and what is needed to determine protection, a commodity can burn in the warehouse. This includes the 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 are 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 the 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 at the highest point. Incorrect selection of ESFR types and pressures can result from these types of misunderstandings.
While ESFR systems may solve many of the more challenging warehouse protection problems against fires, ensuring that the correct type of ESFR is used a full understanding of the commodity and methods of storage in the warehouse. Careful consideration must also be given to the longterm use and range of flexibility expected by the building owner.
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 incorrect ESFR types and/or pressures.
A final consideration as to whether additional ESFR heads should be required below catwalks merits additional testing.