Mark Fletcher speaks to Dan Steppan, a Senior Staff Engineer with UL, to discover how warehousing and storage facilities are assessed for fire risks and firefighting equipment. He discovers that there are multiple factors involved in the assessment, as well as multiple approaches to addressing potential risks
Dan really knows his stuff: “I’ve been working with warehouse sprinkler systems my whole career here at UL and I’ve seen an incredible array of tests and technology go through our facility. The building in which I do most of my testing is a one-of-a-kind structure developed specifically to assess warehouse fire protection. We use it for the evaluation of warehouses and industrial plant fire sprinkler systems as they have similar risk management issues.”
The large-scale laboratory in which he works measures 36.5 x 36.5 m (120 x 120 ft) and is 18.3m (60 ft) tall. “We also have a moveable 30.5 x 30.5 m (100 x 100 ft) ceiling, which can be positioned anywhere, ranging from 2.4 m (8 ft) to 14.6 m (48 ft) in the air. The moveable ceiling plays a core role in our fire assessment activities as different warehouses have different ceiling heights and over the many years we have been doing these tests we have proved that the ceiling height plays a huge part in a fire’s dynamics. This truly is a unique test area and we can accomplish many things at the push of a button.”
Dan works with a number of stakeholders, including sprinkler manufacturers who are looking for certifications, the insurance industry, which has many concerns over what they are insuring and finally end users – owners of distribution centres and warehouses as well as manufacturing locations (for both parts and warehousing) including those that produce combustible products.
“The primary standard we use in these evaluations,” he continues, “is the National Fire Protection Association’s NFPA13, which covers the installation of sprinkler systems. NFPA documents are well used in Europe and in the Middle East and Asia. There are of course other standards, both national and international, but they follow very similar testing regimens and have a similar set of demands and results. The primary job in relation to this standard is related to industrial fires and it asks the question, ‘once a fire starts, will the sprinkler systems be adequate to deal with it’.”
UL and NFPA13 define a commodity classification as the basis of the measurement system used in the test methodology. “An insurance company would go in and look around a site to assess the hazard of the products in the warehouse using NFPA13. This provides a wide path to lock down hazards, which can be anything from low, Class 1 commodity, such as non-combustible materials in wooden crates. The class level then increases from Class 2 through to Class 4 as the amount of combustible materials increase.
“Class 2 may typically be corrugated board (cardboard) boxes with minimal combustibles inside,” he adds, “with plastic packaging and products – which burn significantly hotter – taking the Class levels up to 3 or 4. Plastics have their own sub categories. The lowest being unexpanded Group A plastics, such as hard plastic cups inside a corrugated box, up to expanded plastics – including Styrofoam that is used for product protection – that burn very well. All of these categories are defined in NFPA13.”
Once the class of the product and packaging has been defined, the stakeholders can then determine how much water the sprinkler system needs to supply. “So the definition of different products and their packaging is key to understanding if the existing system is adequate, if not either the insurance rates become higher or the sprinkler system gets upgraded.”
“A lot of what we do requires large scale testing of a portion of a warehouse full of products, but we also offer another test that allows us to assign hazard-class rankings to specific products,” Steppan elaborates. “Warehouse owners and fire marshals may not understand how a product is created and the issues associated with creative packaging; and guidance may simply not exist. What we can do is test a product to ascertain the rating. But it is not just the product defining the hazard class. We look at the makeup of the product and what materials are involved, as each may have a different role in the overall hazard class. If we look at a stuffed toy, for example, the product itself has a plastic outer shell and plastic beads internally (which burn really well). One could consider the toy to be an expanded plastic (fur outer shell) or unexpanded (internal beads), so the customer may not know how to rank it and if their sprinkler system was between the two, they may want to do a test with us.”
When UL does a test it deploys eight full pallet loads of products. “The classification rank is not just for the product, but also the box, any secondary packaging and the support platform on which the secondary packaging sits – such as a wooden or plastic pallet. Quite often the packaging and content will conflict in terms of ratings. An example will be appliances, stored in cardboard boxes with styrofoam packaging. A metal washing machine is not inherently that combustible, but its packaging is. The product maybe Class 1 or 2, whereas the packaging will be expanded plastic.
“We use 24 pallet loads of product in total, in order to perform three tests (8 pallet loads each). We burn the product and then apply water when a sprinkler would have activated. The test demonstrates how the products react with water,” he continues. “We do three different tests relating to water levels from low levels, where the fire continues to burn, through to higher level of water where the fire is fully controlled or even suppressed to the point of extinguishment. As long as we can understand what water levels are needed, we can then assign a hazard class. Big box stores are hugely impacted; and sometimes we get manufacturers coming to us to look at different packaging schemes, as they understand that different packaging can have different penalties, either for them or their customers.
“We also have a category for plastic pallets, which burn much hotter than wood,” Steppan continues. “We use our own standard – UL 2335 – to look at plastic pallets in order to assess flammability and the effectiveness of fire retardants, which are added to make them burn in a way similar to or lower than wooden pallets when sprinkler systems are employed.”
Plastic pallets are being used more and more – especially in taller, automated warehouses – due to the fact that wooden pallet can break or splinter and jam the automated systems. The food industry is also using them more frequently due to cleanliness issues (washability). Another reason for the use of plastics is due to the proliferation of RFID technology, which does have limitations with wooden pallets that may have picked up moisture from the atmosphere.
Within NFPA13, non-approved plastic pallets attract a penalty, increasing classifications by one or two classes. Steel reinforced plastic pallets are even worse as they can keep the product in the racking for longer periods of time. With non-reinforced pallets, the product may fall through the racks and subsequently be better protected by the discharging water.
“There are always interesting scenarios,” Steppan explains. “When a beer manufacturer came to us, they had a Class 1 commodity product, but they wanted to use reinforced plastic pallets – and this would have meant a move from Class 1 to Class 3. They came to us and argued ‘we have a lot of water in our product… how does this water content affect the pallet’s classification?’ We tested cans and glass bottles and discovered that the liquid in the beer was able to ‘help’ keep any fires under control, so the brewer was able to make a case for maintaining a Class 1 status, even though NFPA13 says they should have a 2-class penalty. There is a paragraph in NFPA13 that states when there’s an unknown hazard class, you can go to a nationally recognised test laboratory to evaluate hazard classification’. It’s rare that the testing allows for a lower classification, but with in-depth testing it can make a difference.
“Other variations can include mixed storage areas,” he continues. “NFPA13 allows you segregate areas, using firewalls and compartmented spaces in order define different classification areas, but as a general rule, you protect for the highest classification. Insurance companies may also have data that might allow further reductions, but that typically comes as part of large-scale fire testing.”
“NFPA13 is on three-year revision cycle and this allows it to evolve to cover new technologies and new materials. One example would be the recent proliferation of lithium ion batteries. This is challenging from a suppression standpoint,” Steppan explains, “as we can see both fires and rocketing of the burning batteries due to their effectively being combustible liquids in a metal container. In cases like this we evaluate the product and firefighting technology in order to create or improve acceptable suppression procedures.
“Looking to the future, NFPA13 has the provision for larger K factor (flow vs. pressure) sprinklers due to the fact that taller warehouses need more water to get from ceiling to floor. Sprinkler system effectiveness is often helped by the deployment of rack-based sprinklers. Another technology being proposed for warehouses is lowered-oxygen environments, into which typically only robots would venture. This is in its infancy in terms of standardisation, but we are aware of this approach and its current deployment in data centres; it is only a matter of time before we see it being used more and more in warehousing operations.”
NFPA13 may have found its roots in 1896, but it still forms an intrinsic part of testing regimens for many variations of industrial premises. Like all standards, it is not set in stone and through effective supplementary testing, such as that carried out by UL, owner/operators can gain a bit of flexibility from their insurers. It is great to see that even the old standards still carry weight, thanks in part to the impressive work undertaken by UL, associated stakeholders and all their worldwide peers.
This article was published in ‘International Fire Buyer‘ published by Hand Media