ESFR Sprinklers The Perfect Solution To Warehouse Fire Protection?
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 2010 Edition, Section 220.127.116.11 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. 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).|
|Question:||Once an ESFR system is installed, can any business move in and store however they want?|
|Answer:||No. For example, with one exception (NFPA 13, Table 15.4.1), ESFR systems cannot be applied to storage of exposed (uncartoned) expanded Group A Plastics. Also each type of ESFR head can protect a different set of commodities. For example, K-25 ESFR cannot protect cartoned expanded plastics (such as products that have >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 products such as mattresses, pillows, synthetic foam packaging (non-starch based), etc. 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 sprinkler systems required below catwalks if the overhead system is ESFR?|
|Answer:||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 Data sheet 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 Global Data Sheets 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 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, Section 18.104.22.168.3 Exceptions 1-3 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.|
|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:
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 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 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.
(updated on Dec 10th 2010)