Our last column discussed special purpose warehouses with a focus on flammable and combustible liquids storage. This article continues that discussion with a focus on cold storage (freezer) warehouses. As we stated before, there is a growing concern among fire departments about conducting offensive fire fighting operations at industrial properties where everyone is safely out of the building. We cited National Fire Protection Association (NFPA) 1500 Standard on Fire Department Occupational Safety and Health Program which states in A.8.3.2: “We will risk our lives a LITTLE, in a calculated manner, to save SAVABLE property.”
We stated that there is considerable discussion surrounding what is savable. A primary purpose of this series of articles, since inception, has been to help facility managers and fire departments to be able to analyze their risks through pre-fire planning. Our basic premise is that facilities that are properly protected, which for the purposes of this article means with adequate sprinklers, are usually savable. Guidance on determining what is adequate has been presented in past articles. A property loss prevention or fire protection engineer may need to be engaged to determine the adequacy of the sprinklers.
We need to state up front that freezer warehouses do burn, as any insurer or large operator of them can attest. It is important not to get talked into the widely held misconception that they cannot burn because it is too cold. All of the issues cited in parts 1 and 2 regarding general purpose warehouses still apply but are exacerbated for the following reasons:
• insulated metal panels (sandwich panels) or other insulation is used which increases the combustibility of the structure. The need for heavy insulation also limits the ability to provide smoke and heat vents.
• less operational experience for firefighters to draw from and also against which to evaluate the adequacy of published standards against real fires.
• more complicated fire protection systems such as double- interlock preaction systems and Early Suppression Fast Response Sprinklers (ESFR) using antifreeze.
• fire protection systems that are susceptible to ice plugs in the piping.
• ammonia refrigeration which is both a hazmat and explosion hazard.
• extremely low temperatures.
Discussion: John.Frank@xlgroup.com or at (404) 431-2673.
Large commercial freezers typically use anhydrous ammonia as a refrigerant. The hazmat response implications of an ammonia release are beyond the scope of this article. As has been the focus of our articles, our intent is to discuss topics which are not commonly addressed in the fire service literature or training programs. Many industrial hazmat programs do an excellent job of addressing the hazmat response to such an incident.
If the installed fire protection systems fail to control a fire, then a roof collapse with ensuing ammonia release could occur. Therefore, a major concern is to determine if the sprinklers can control a fire so that damage to the ammonia system does not occur or is at the very least significantly minimized.
If the system cannot control a fire, a major hazmat incident is possible in conjunction with a major fire. Knowledge of the system, including locations of tanks, system capacity, pumps, shutoffs and piping layout allows the fire department to make an informed decision on whether or not offensive intervention is practical.
Freezer warehouses may not be sprinklered at all in of the belief that they cannot burn. Sprinkler systems that do exist may not be adequate. Improperly installed or maintained sprinkler systems can also develop ice plugs which block water discharge. Without properly functioning sprinklers, the fire service probably will not be able to control the fire.
Proper sprinkler design and ice plug prevention are discussed in freezer protection standards such as NFPA 13, Standard for the Installation of Sprinkler Systems, GAP 10.2.11, Refrigerated Storage and Warehousing, and FM Data Sheet 8-29, Refrigerated Storage. Ice plug prevention is extremely important and something of which many readers may be unaware. For example, there are installation guidelines that are intended to reduce the occurrence of ice plugs. They include pipe sections that can be easily removed to inspect for ice plugs. Details are beyond the scope of this article but it is important to be aware of the issue.
Simple dry pipe sprinkler systems, commonly found on loading docks, are not appropriate for most freezer warehouses. This is because, if the system trips accidentally, the pipes will fill with water and freeze before the system can drain. Then, the system may have to be disassembled, taken to a warm area or outside to thaw, and then reinstalled. The cost and impairment time are obviously unacceptable.
Instead, a double interlock pre-action system is frequently installed. With this kind of system, a heat detector and a sprinkler must both activate before the pipes fill with water. This minimizes the chance of an accidental trip but significantly complicates system design, installation and maintenance.
In-rack sprinklers are frequently required in high rack storage. Experience has shown that a forklift operator can damage the heat detection system and the sprinkler piping at the same time. This will cause even a double interlock system to trip and fill the pipe with water; which will quickly freeze. After this has happened a time or two, the warehouse operator may just leave the system frozen. This of course means that it will not function during a fire.
To avoid the problems associated with in-rack sprinklers, other types of systems such as early suppression fast response (ESFR) antifreeze systems, ESFR dry pendant systems, and enhancements to conventional double interlock systems that eliminate the need for in-rack sprinklers have been developed. They each have their own special design, installation, and maintenance requirements. A detailed review of the system by an experienced engineer is essential. Testing and maintenance also requires special expertise that many sprinkler maintenance contractors will not have.
An unusual feature of freezer warehouses is that sprinklers to protect the insulated walls may be necessary. Details are provided in FM Data Sheet 8-29, Refrigerated Storage.
The fire service should ask questions about the basis for the design, and what kind of engineering review has been done. They should inquire about ice plug prevention, system testing and maintenance, and ensure that the system is not tripped and frozen. Because these systems are more complicated than traditional wet or dry pipe systems, there are more opportunities for failure.
Assuming that the sprinkler design is adequate and the system functions properly, the low temperatures will still complicate operations. Even with a fire burning (but controlled by the sprinklers), the temperature in the surrounding area can still be very cold. Visibility due to smoke is often a problem at warehouse fires. At freezer warehouse fires, firefighters have reported a fog- like environment due to condensing/freezing water vapor in addition to the smoke.
Ice can accumulate on racks, which adds to their load and could lead to a rack collapse. Ice can also build up on the floor making overhaul difficult. Forklifts are often used to unload damaged commodities to take them outside. Forklift operations on an icy floor can obviously be problematic.
Sometimes the freezer is actually a “building within a building” with a small interstitial space or gap on all sides of the freezer compartment. This complicates forcible entry, ventilation, and could provide an avenue for hidden flame spread.
We invite the fire service and warehouse operators to share their experiences with these issues and how they were managed.
Facilities with freezer warehouses warrant the highest degree of technical pre-planning and regular visits to ensure that storage is in accordance with system design.
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John Frank, P.E., CFPS is with XL Global Asset Protection Services, LLP (XL GAPS), a property loss prevention consulting firm and an XL Group company. The XL Group plc, through its operating subsidiaries, is a leading provider of global insurance and reinsurance coverages to industrial, commercial and professional service firms, insurance companies and other enterprises on a worldwide basis. More information about XL GAPS is available at www.xlgaps.com and more information about XL Group plc is available at www.xlgroup.com.