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This month we have one of the Society of Fire Protection Engineer’s active committee members writing on the use of ESFR sprinklers. They are very common in the protection of storage, but that does not mean they can be used to protect every combination of building height, storage height, commodity and storage arrangement. Read on to learn about some situations where ESFR may not be the ideal choice for active protection.
Early suppression fast response (ESFR) sprinklers provide fire protection professionals a powerful tool, especially in preventing warehouse losses. ESFR sprinklers were designed to protect a variety of commodities without the need for in-rack sprinklers. For that reason, after their development in the 1980s, ESFRs became the sprinkler of choice by many warehouse developers.
Unfortunately, the ESFR sprinklers’ reputation as a one-size-fits-all protection solution has created confusion amongst many in the construction and real estate industry. As one broker asked me, “This building has ESFR sprinklers, so why is the fire marshal denying my C of O? Can’t my tenant do anything he wants?”
The answer, of course, is, “It depends.”
The purpose of this article is to remind the fire protection industry of some limitations of ESFR sprinkler protection and describe some situations where ESFR sprinklers may not be an option to protect a warehouse occupancy. These examples include the protection of certain commodities, as well as installation into buildings with older fire protection features that were once commonly constructed but more recently have been shown to impact fire sprinkler performance negatively.
Commodity, Storage Configuration Challenges
Although ESFR sprinklers provide adequate protection on a wide range of products, some products and certain types of storage configurations are not permitted with this type of protection. Let’s investigate a few different forbidden scenarios.
The first commodity challenge is flammable and combustible liquids, such as cleaners, fuels and solvents. NFPA 30 annex language warns users to use only those ESFR sprinklers tested for the protection of liquids as reflected in the protection tables. Those tables list precise container sizes and materials, sprinkler K-factors, storage and ceiling heights, and in-rack sprinkler requirements.
For example, for Class IIIB through IB flammable/combustible liquids stored in relieving metal containers, a maximum storage height of 14 feet with a maximum 24-foot ceiling height is permitted when K-14 and larger orifice ESFR sprinklers are installed at the ceiling, in addition to K-11.2 in-rack sprinklers. The good news is the ceiling sprinkler discharge pressure is specified to be, at minimum, 50 psi, identical to the requirement for starting pressure in NFPA 13 for a 25-foot ceiling protecting Group A plastics.
Unfortunately, the in-rack sprinkler flow must be added to the ceiling sprinkler flow. Typically, this increased flow demand results in upsized piping and upgrades to the water supply via a fire pump addition.
A second storage challenge is open-top containers stored above the lowest level of a rack. The primary concern is that the open-top containers will catch the sprinkler discharge and minimize the water flow to the lowest level of the rack. A secondary concern is the additional weight of the trapped water will overload the rack and cause a collapse.
Note that the open-top containers may either have wire mesh or slotted sides and bottoms or a fixed lid in their stored locations to mitigate the open-top container concern.
A third, very common commodity challenge is exposed expanded plastics, such as mattresses, packing peanuts, and foam cups and plates. Some surprising commodities also classified as exposed expanded plastics include charcoal impregnated with lighter fluid and athletic shoes. Exposed expanded plastics protection was added to the 2016 edition of NFPA 13, but there are many limitations.
For example, solid vertical barriers and wire mesh shelving are required and K25.2 ESFR sprinklers must be installed. These limitations make it unlikely that a facility built before 2017 would be permitted to store these plastics without significant modification to the sprinkler system.
Building Envelope Challenges
In general, ESFR sprinklers are appropriate for installation in warehouses with a maximum 45-foot ceiling height and 40-foot maximum storage height. Some sprinklers have approvals to store higher, but we’re focusing on the current parameters stated in NFPA and FM Global Data Sheet installation standards. For those applications with higher ceiling heights, follow the manufacturer installation instructions, as applicable.
A couple of building features once commonly installed in warehouses that negatively impact ESFR sprinkler performance are draft curtains, and smoke and heat vents. Both of these building features have been shown in full-scale fire testing to negatively impact sprinkler performance (NFPA 13, Table C-22) by interfering with the movement of heated air at the ceiling. As a result, ESFR sprinklers shall not be installed in any facility fitted with draft curtains (NFPA 13, 18.104.22.168).
Smoke and heat vents may be installed with ESFR sprinklers but they must be carefully specified. Two options exist. The first option is to install manually operated smoke and heat vents. The second option is the installation of vents using a “high-temperature rated, standard-response operating mechanism.” (NFPA 13, 22.214.171.124 and 126.96.36.199) Both of these options allow the ESFR sprinklers to actuate and operate as originally designed.
Another building envelope challenge involves buildings greater than 40-foot high. Some sprinkler configurations once allowed as recently as the 2016 edition of NFPA 13 have been removed. For example, when protecting rack storage, NFPA 13 requires both K-14 and K-16.8 ESFRs to have in-rack sprinklers installed when ceiling heights are at a maximum of 40 feet (NFPA 13, Tables 23.5.1 and 23.6.1) and not permitted where ceiling heights exceed 40 feet.
As a result, shell warehouses constructed with ESFR sprinkler systems just a few years ago may no longer comply with NFPA 13 requirements without significant modification, depending on the desired arrangement and commodities of the actual occupant.
Although ESFR sprinklers can provide adequate protection for a wide-ranging variety of storage commodities and configurations, it is essential to remember that these sprinklers are not one-size-fits-all. Building owners, tenants and AHJs must carefully consider the proposed commodity and packaging to be stored along with the physical arrangement. Contact a fire protection professional for assistance if there is any concern about the adequacy of the ESFR sprinkler system.